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 $67.43   7.551%   $72.5216   $72.52   $72.50   $72.50  
  Purchase #2 $53.48   10.694%   $59.1992   $59.20   $59.20   $59.20  
  Purchase #3 $231.32   11.811%   $258.6412   $258.64   $258.65   $258.60  
  Purchase #4 $235.41   9.533%   $257.8516   $257.85   $257.85   $257.90  
  Purchase #5 $242.74   6.818%   $259.29   $259.29   $259.30   $259.30  
  Purchase #6 $200.67   6.234%   $213.1798   $213.18   $213.20   $213.20  
  Purchase #7 $40.29   6.614%   $42.9548   $42.95   $42.95   $43.00  
  7 purchase totals = $1,071.34       $1,163.6382   $1,163.63   $1,163.65   $1,163.70