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 $64.97   7.564%   $69.8843   $69.88   $69.90   $69.90  
  Purchase #2 $230.71   4.828%   $241.8487   $241.85   $241.85   $241.80  
  Purchase #3 $15.70   5.140%   $16.507   $16.51   $16.50   $16.50  
  Purchase #4 $206.68   12.352%   $232.2091   $232.21   $232.20   $232.20  
  Purchase #5 $214.62   3.108%   $221.2904   $221.29   $221.30   $221.30  
  Purchase #6 $25.83   7.516%   $27.7714   $27.77   $27.75   $27.80  
  Purchase #7 $182.70   9.795%   $200.5955   $200.60   $200.60   $200.60  
  7 purchase totals = $941.21       $1,010.1064   $1,010.11   $1,010.10   $1,010.10