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 $56.73   9.468%   $62.1012   $62.10   $62.10   $62.10  
  Purchase #2 $201.64   8.641%   $219.0637   $219.06   $219.05   $219.10  
  Purchase #3 $239.32   10.555%   $264.5802   $264.58   $264.60   $264.60  
  Purchase #4 $94.50   8.145%   $102.197   $102.20   $102.20   $102.20  
  Purchase #5 $232.72   10.262%   $256.6017   $256.60   $256.60   $256.60  
  Purchase #6 $149.85   3.354%   $154.876   $154.88   $154.90   $154.90  
  Purchase #7 $227.89   7.296%   $244.5169   $244.52   $244.50   $244.50  
  7 purchase totals = $1,202.65       $1,303.9367   $1,303.94   $1,303.95   $1,304.00