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 $211.52   9.690%   $232.0163   $232.02   $232.00   $232.00  
  Purchase #2 $52.74   11.845%   $58.9871   $58.99   $59.00   $59.00  
  Purchase #3 $233.31   5.847%   $246.9516   $246.95   $246.95   $247.00  
  Purchase #4 $79.97   12.248%   $89.7647   $89.76   $89.75   $89.80  
  Purchase #5 $209.38   4.699%   $219.2188   $219.22   $219.20   $219.20  
  Purchase #6 $79.82   9.745%   $87.5985   $87.60   $87.60   $87.60  
  Purchase #7 $144.65   5.380%   $152.4322   $152.43   $152.45   $152.40  
  7 purchase totals = $1,011.39       $1,086.9692   $1,086.97   $1,086.95   $1,087.00