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 $38.88   11.160%   $43.219   $43.22   $43.20   $43.20  
  Purchase #2 $238.63   12.306%   $267.9958   $268.00   $268.00   $268.00  
  Purchase #3 $62.52   8.725%   $67.9749   $67.97   $67.95   $68.00  
  Purchase #4 $48.89   4.281%   $50.983   $50.98   $51.00   $51.00  
  Purchase #5 $211.58   3.825%   $219.6729   $219.67   $219.65   $219.70  
  Purchase #6 $160.55   3.524%   $166.2078   $166.21   $166.20   $166.20  
  Purchase #7 $234.89   13.402%   $266.37   $266.37   $266.35   $266.40  
  7 purchase totals = $995.94       $1,082.4234   $1,082.42   $1,082.35   $1,082.50