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 $58.40   6.735%   $62.3332   $62.33   $62.35   $62.30  
  Purchase #2 $244.52   11.404%   $272.4051   $272.41   $272.40   $272.40  
  Purchase #3 $149.97   10.656%   $165.9508   $165.95   $165.95   $166.00  
  Purchase #4 $71.72   5.117%   $75.3899   $75.39   $75.40   $75.40  
  Purchase #5 $32.35   11.661%   $36.1223   $36.12   $36.10   $36.10  
  Purchase #6 $237.98   13.512%   $270.1359   $270.14   $270.15   $270.10  
  Purchase #7 $165.58   7.767%   $178.4406   $178.44   $178.45   $178.40  
  7 purchase totals = $960.52       $1,060.7778   $1,060.78   $1,060.80   $1,060.70