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 $180.33   8.153%   $195.0323   $195.03   $195.05   $195.00  
  Purchase #2 $95.52   4.356%   $99.6809   $99.68   $99.70   $99.70  
  Purchase #3 $46.69   3.752%   $48.4418   $48.44   $48.45   $48.40  
  Purchase #4 $246.64   12.404%   $277.2332   $277.23   $277.25   $277.20  
  Purchase #5 $70.90   6.207%   $75.3008   $75.30   $75.30   $75.30  
  Purchase #6 $204.35   5.363%   $215.3093   $215.31   $215.30   $215.30  
  Purchase #7 $39.37   3.820%   $40.8739   $40.87   $40.85   $40.90  
  7 purchase totals = $883.80       $951.8722   $951.86   $951.90   $951.80