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 $85.35   11.846%   $95.4606   $95.46   $95.45   $95.50  
  Purchase #2 $83.69   4.357%   $87.3364   $87.34   $87.35   $87.30  
  Purchase #3 $247.42   4.285%   $258.0219   $258.02   $258.00   $258.00  
  Purchase #4 $98.41   5.445%   $103.7684   $103.77   $103.75   $103.80  
  Purchase #5 $31.67   11.252%   $35.2335   $35.23   $35.25   $35.20  
  Purchase #6 $146.52   9.588%   $160.5683   $160.57   $160.55   $160.60  
  Purchase #7 $174.36   9.707%   $191.2851   $191.29   $191.30   $191.30  
  7 purchase totals = $867.42       $931.6742   $931.68   $931.65   $931.70