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 $74.51   10.546%   $82.3678   $82.37   $82.35   $82.40  
  Purchase #2 $235.29   12.573%   $264.873   $264.87   $264.85   $264.90  
  Purchase #3 $112.80   12.764%   $127.1978   $127.20   $127.20   $127.20  
  Purchase #4 $25.89   3.754%   $26.8619   $26.86   $26.85   $26.90  
  Purchase #5 $133.94   9.324%   $146.4286   $146.43   $146.45   $146.40  
  Purchase #6 $204.45   3.198%   $210.9883   $210.99   $211.00   $211.00  
  Purchase #7 $224.71   5.298%   $236.6151   $236.62   $236.60   $236.60  
  7 purchase totals = $1,011.59       $1,095.3325   $1,095.34   $1,095.30   $1,095.40