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 $60.86   3.569%   $63.0321   $63.03   $63.05   $63.00  
  Purchase #2 $193.65   5.111%   $203.5475   $203.55   $203.55   $203.50  
  Purchase #3 $49.56   3.305%   $51.198   $51.20   $51.20   $51.20  
  Purchase #4 $142.57   10.327%   $157.2932   $157.29   $157.30   $157.30  
  Purchase #5 $191.32   5.689%   $202.2042   $202.20   $202.20   $202.20  
  Purchase #6 $25.82   3.552%   $26.7371   $26.74   $26.75   $26.70  
  Purchase #7 $44.65   8.131%   $48.2805   $48.28   $48.30   $48.30  
  7 purchase totals = $708.43       $752.2926   $752.29   $752.35   $752.20