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 $237.84   12.374%   $267.2703   $267.27   $267.25   $267.30  
  Purchase #2 $195.83   7.289%   $210.104   $210.10   $210.10   $210.10  
  Purchase #3 $247.57   3.250%   $255.616   $255.62   $255.60   $255.60  
  Purchase #4 $182.58   13.239%   $206.7518   $206.75   $206.75   $206.80  
  Purchase #5 $184.64   5.552%   $194.8912   $194.89   $194.90   $194.90  
  Purchase #6 $188.50   8.700%   $204.8995   $204.90   $204.90   $204.90  
  Purchase #7 $111.35   9.594%   $122.0329   $122.03   $122.05   $122.00  
  7 purchase totals = $1,348.31       $1,461.5657   $1,461.56   $1,461.55   $1,461.60