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 $58.64   10.723%   $64.928   $64.93   $64.95   $64.90  
  Purchase #2 $245.36   4.188%   $255.6357   $255.64   $255.65   $255.60  
  Purchase #3 $161.38   3.533%   $167.0816   $167.08   $167.10   $167.10  
  Purchase #4 $202.43   9.816%   $222.3005   $222.30   $222.30   $222.30  
  Purchase #5 $203.52   8.165%   $220.1374   $220.14   $220.15   $220.10  
  Purchase #6 $217.94   6.604%   $232.3328   $232.33   $232.35   $232.30  
  Purchase #7 $201.46   10.222%   $222.0532   $222.05   $222.05   $222.10  
  7 purchase totals = $1,290.73       $1,384.4692   $1,384.47   $1,384.55   $1,384.40