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 $193.33   3.553%   $200.199   $200.20   $200.20   $200.20  
  Purchase #2 $66.90   3.866%   $69.4864   $69.49   $69.50   $69.50  
  Purchase #3 $202.33   4.873%   $212.1895   $212.19   $212.20   $212.20  
  Purchase #4 $129.48   11.352%   $144.1786   $144.18   $144.20   $144.20  
  Purchase #5 $123.57   9.473%   $135.2758   $135.28   $135.30   $135.30  
  Purchase #6 $240.32   4.270%   $250.5817   $250.58   $250.60   $250.60  
  Purchase #7 $74.85   11.602%   $83.5341   $83.53   $83.55   $83.50  
  7 purchase totals = $1,030.78       $1,095.4451   $1,095.45   $1,095.55   $1,095.50