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 $58.33   11.380%   $64.968   $64.97   $64.95   $65.00  
  Purchase #2 $160.52   13.303%   $181.874   $181.87   $181.85   $181.90  
  Purchase #3 $50.88   5.185%   $53.5181   $53.52   $53.50   $53.50  
  Purchase #4 $7.67   12.814%   $8.6528   $8.65   $8.65   $8.70  
  Purchase #5 $124.70   6.113%   $132.3229   $132.32   $132.30   $132.30  
  Purchase #6 $92.97   6.430%   $98.948   $98.95   $98.95   $98.90  
  Purchase #7 $211.51   5.363%   $222.8533   $222.85   $222.85   $222.90  
  7 purchase totals = $706.58       $763.1371   $763.13   $763.05   $763.20