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 $67.92   10.323%   $74.9314   $74.93   $74.95   $74.90  
  Purchase #2 $202.43   11.185%   $225.0718   $225.07   $225.05   $225.10  
  Purchase #3 $82.41   11.458%   $91.8525   $91.85   $91.85   $91.90  
  Purchase #4 $187.28   3.165%   $193.2074   $193.21   $193.20   $193.20  
  Purchase #5 $66.83   8.373%   $72.4257   $72.43   $72.45   $72.40  
  Purchase #6 $102.93   3.277%   $106.303   $106.30   $106.30   $106.30  
  Purchase #7 $157.63   12.470%   $177.2865   $177.29   $177.30   $177.30  
  7 purchase totals = $867.43       $941.0783   $941.08   $941.10   $941.10