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 $88.93   4.524%   $92.9532   $92.95   $92.95   $93.00  
  Purchase #2 $209.98   6.267%   $223.1394   $223.14   $223.15   $223.10  
  Purchase #3 $132.41   12.142%   $148.4872   $148.49   $148.50   $148.50  
  Purchase #4 $42.75   13.549%   $48.5422   $48.54   $48.55   $48.50  
  Purchase #5 $193.68   12.377%   $217.6518   $217.65   $217.65   $217.70  
  Purchase #6 $153.61   4.205%   $160.0693   $160.07   $160.05   $160.10  
  Purchase #7 $138.32   11.107%   $153.6832   $153.68   $153.70   $153.70  
  7 purchase totals = $959.68       $1,044.5263   $1,044.52   $1,044.55   $1,044.60