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 $63.63   8.547%   $69.0685   $69.07   $69.05   $69.10  
  Purchase #2 $94.51   10.354%   $104.2956   $104.30   $104.30   $104.30  
  Purchase #3 $197.40   6.363%   $209.9606   $209.96   $209.95   $210.00  
  Purchase #4 $58.29   3.134%   $60.1168   $60.12   $60.10   $60.10  
  Purchase #5 $169.98   7.776%   $183.1976   $183.20   $183.20   $183.20  
  Purchase #6 $250.30   7.209%   $268.3441   $268.34   $268.35   $268.30  
  Purchase #7 $140.94   7.668%   $151.7473   $151.75   $151.75   $151.70  
  7 purchase totals = $975.05       $1,046.7305   $1,046.74   $1,046.70   $1,046.70