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 $201.82   9.617%   $221.229   $221.23   $221.25   $221.20  
  Purchase #2 $173.61   12.277%   $194.9241   $194.92   $194.90   $194.90  
  Purchase #3 $151.28   12.819%   $170.6726   $170.67   $170.65   $170.70  
  Purchase #4 $205.42   3.498%   $212.6056   $212.61   $212.60   $212.60  
  Purchase #5 $60.94   6.257%   $64.753   $64.75   $64.75   $64.80  
  Purchase #6 $61.48   4.807%   $64.4353   $64.44   $64.45   $64.40  
  Purchase #7 $156.65   6.574%   $166.9482   $166.95   $166.95   $166.90  
  7 purchase totals = $1,011.20       $1,095.5678   $1,095.57   $1,095.55   $1,095.50