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 $62.92   4.388%   $65.6809   $65.68   $65.70   $65.70  
  Purchase #2 $245.54   10.823%   $272.1148   $272.11   $272.10   $272.10  
  Purchase #3 $88.89   10.787%   $98.4786   $98.48   $98.50   $98.50  
  Purchase #4 $226.94   10.828%   $251.5131   $251.51   $251.50   $251.50  
  Purchase #5 $110.73   10.582%   $122.4474   $122.45   $122.45   $122.40  
  Purchase #6 $153.73   3.697%   $159.4134   $159.41   $159.40   $159.40  
  Purchase #7 $48.58   11.810%   $54.3173   $54.32   $54.30   $54.30  
  7 purchase totals = $937.33       $1,023.9655   $1,023.96   $1,023.95   $1,023.90