Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $96.47   11.765%   $107.8197   $107.82   $107.80   $107.80  
  Purchase #2 $236.74   8.681%   $257.2914   $257.29   $257.30   $257.30  
  Purchase #3 $145.95   5.274%   $153.6474   $153.65   $153.65   $153.60  
  Purchase #4 $153.93   10.302%   $169.7879   $169.79   $169.80   $169.80  
  Purchase #5 $204.71   5.843%   $216.6712   $216.67   $216.65   $216.70  
  Purchase #6 $95.35   10.791%   $105.6392   $105.64   $105.65   $105.60  
  Purchase #7 $175.66   9.447%   $192.2546   $192.25   $192.25   $192.30  
  7 purchase totals = $1,108.81       $1,203.1114   $1,203.11   $1,203.10   $1,203.10