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 $213.96   8.531%   $232.2129   $232.21   $232.20   $232.20  
  Purchase #2 $31.46   7.608%   $33.8535   $33.85   $33.85   $33.90  
  Purchase #3 $148.55   5.770%   $157.1213   $157.12   $157.10   $157.10  
  Purchase #4 $96.42   8.362%   $104.4826   $104.48   $104.50   $104.50  
  Purchase #5 $188.99   7.191%   $202.5803   $202.58   $202.60   $202.60  
  Purchase #6 $201.69   7.797%   $217.4158   $217.42   $217.40   $217.40  
  Purchase #7 $138.88   8.663%   $150.9112   $150.91   $150.90   $150.90  
  7 purchase totals = $1,019.95       $1,098.5776   $1,098.57   $1,098.55   $1,098.60