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 $68.81   4.808%   $72.1184   $72.12   $72.10   $72.10  
  Purchase #2 $119.56   5.272%   $125.8632   $125.86   $125.85   $125.90  
  Purchase #3 $202.56   9.180%   $221.155   $221.16   $221.15   $221.20  
  Purchase #4 $213.63   5.568%   $225.5249   $225.52   $225.50   $225.50  
  Purchase #5 $98.74   8.472%   $107.1053   $107.11   $107.10   $107.10  
  Purchase #6 $64.39   11.826%   $72.0048   $72.00   $72.00   $72.00  
  Purchase #7 $247.64   7.663%   $266.6167   $266.62   $266.60   $266.60  
  7 purchase totals = $1,015.33       $1,090.3883   $1,090.39   $1,090.30   $1,090.40