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 $60.53   3.471%   $62.631   $62.63   $62.65   $62.60  
  Purchase #2 $110.39   11.288%   $122.8508   $122.85   $122.85   $122.90  
  Purchase #3 $65.28   13.648%   $74.1894   $74.19   $74.20   $74.20  
  Purchase #4 $222.34   5.623%   $234.8422   $234.84   $234.85   $234.80  
  Purchase #5 $204.36   8.817%   $222.3784   $222.38   $222.40   $222.40  
  Purchase #6 $138.53   10.522%   $153.1061   $153.11   $153.10   $153.10  
  Purchase #7 $68.92   5.778%   $72.9022   $72.90   $72.90   $72.90  
  7 purchase totals = $870.35       $942.9001   $942.90   $942.95   $942.90