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 $43.65   6.703%   $46.5759   $46.58   $46.60   $46.60  
  Purchase #2 $221.39   10.234%   $244.0471   $244.05   $244.05   $244.00  
  Purchase #3 $22.77   9.600%   $24.9559   $24.96   $24.95   $25.00  
  Purchase #4 $137.65   10.469%   $152.0606   $152.06   $152.05   $152.10  
  Purchase #5 $227.28   11.324%   $253.0172   $253.02   $253.00   $253.00  
  Purchase #6 $151.35   8.356%   $163.9968   $164.00   $164.00   $164.00  
  Purchase #7 $74.63   11.855%   $83.4774   $83.48   $83.50   $83.50  
  7 purchase totals = $878.72       $968.1309   $968.15   $968.15   $968.20