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 $68.80   9.523%   $75.3518   $75.35   $75.35   $75.40  
  Purchase #2 $245.73   6.351%   $261.3363   $261.34   $261.35   $261.30  
  Purchase #3 $58.74   6.536%   $62.5792   $62.58   $62.60   $62.60  
  Purchase #4 $220.93   10.557%   $244.2536   $244.25   $244.25   $244.30  
  Purchase #5 $14.80   3.180%   $15.2706   $15.27   $15.25   $15.30  
  Purchase #6 $207.69   3.529%   $215.0194   $215.02   $215.00   $215.00  
  Purchase #7 $111.79   8.482%   $121.272   $121.27   $121.25   $121.30  
  7 purchase totals = $928.48       $995.0829   $995.08   $995.05   $995.20