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 $60.97   5.437%   $64.2849   $64.28   $64.30   $64.30  
  Purchase #2 $196.81   7.343%   $211.2618   $211.26   $211.25   $211.30  
  Purchase #3 $5.53   4.706%   $5.7902   $5.79   $5.80   $5.80  
  Purchase #4 $242.92   4.513%   $253.883   $253.88   $253.90   $253.90  
  Purchase #5 $119.51   5.412%   $125.9779   $125.98   $126.00   $126.00  
  Purchase #6 $247.39   5.460%   $260.8975   $260.90   $260.90   $260.90  
  Purchase #7 $118.66   7.871%   $127.9997   $128.00   $128.00   $128.00  
  7 purchase totals = $991.79       $1,050.0950   $1,050.09   $1,050.15   $1,050.20