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 $35.25   6.601%   $37.5769   $37.58   $37.60   $37.60  
  Purchase #2 $176.94   4.194%   $184.3609   $184.36   $184.35   $184.40  
  Purchase #3 $44.85   7.419%   $48.1774   $48.18   $48.20   $48.20  
  Purchase #4 $208.37   12.580%   $234.5829   $234.58   $234.60   $234.60  
  Purchase #5 $39.83   8.280%   $43.1279   $43.13   $43.15   $43.10  
  Purchase #6 $62.89   3.496%   $65.0886   $65.09   $65.10   $65.10  
  Purchase #7 $176.51   3.136%   $182.0454   $182.05   $182.05   $182.00  
  7 purchase totals = $744.64       $794.9600   $794.97   $795.05   $795.00