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 $211.41   7.537%   $227.344   $227.34   $227.35   $227.30  
  Purchase #2 $54.78   7.865%   $59.0884   $59.09   $59.10   $59.10  
  Purchase #3 $38.39   12.458%   $43.1726   $43.17   $43.15   $43.20  
  Purchase #4 $112.52   8.846%   $122.4735   $122.47   $122.45   $122.50  
  Purchase #5 $167.45   7.528%   $180.0556   $180.06   $180.05   $180.10  
  Purchase #6 $59.77   7.386%   $64.1846   $64.18   $64.20   $64.20  
  Purchase #7 $231.92   9.114%   $253.0572   $253.06   $253.05   $253.10  
  7 purchase totals = $876.24       $949.3759   $949.37   $949.35   $949.50