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 $82.59   4.757%   $86.5188   $86.52   $86.50   $86.50  
  Purchase #2 $117.91   9.403%   $128.9971   $129.00   $129.00   $129.00  
  Purchase #3 $53.83   11.627%   $60.0888   $60.09   $60.10   $60.10  
  Purchase #4 $186.49   7.203%   $199.9229   $199.92   $199.90   $199.90  
  Purchase #5 $49.82   10.352%   $54.9774   $54.98   $55.00   $55.00  
  Purchase #6 $59.58   4.199%   $62.0818   $62.08   $62.10   $62.10  
  Purchase #7 $147.77   13.795%   $168.1549   $168.15   $168.15   $168.20  
  7 purchase totals = $697.99       $760.7417   $760.74   $760.75   $760.80