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 $87.81   10.504%   $97.0336   $97.03   $97.05   $97.00  
  Purchase #2 $141.85   12.234%   $159.2039   $159.20   $159.20   $159.20  
  Purchase #3 $58.92   5.873%   $62.3804   $62.38   $62.40   $62.40  
  Purchase #4 $185.78   13.835%   $211.4827   $211.48   $211.50   $211.50  
  Purchase #5 $183.29   9.537%   $200.7704   $200.77   $200.75   $200.80  
  Purchase #6 $77.97   13.655%   $88.6168   $88.62   $88.60   $88.60  
  Purchase #7 $190.96   8.662%   $207.501   $207.50   $207.50   $207.50  
  7 purchase totals = $926.58       $1,026.9888   $1,026.98   $1,027.00   $1,027.00