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 $46.67   7.396%   $50.1217   $50.12   $50.10   $50.10  
  Purchase #2 $223.94   9.844%   $245.9847   $245.98   $246.00   $246.00  
  Purchase #3 $211.87   9.203%   $231.3684   $231.37   $231.35   $231.40  
  Purchase #4 $106.44   10.375%   $117.4832   $117.48   $117.50   $117.50  
  Purchase #5 $60.92   3.416%   $63.001   $63.00   $63.00   $63.00  
  Purchase #6 $205.42   10.504%   $226.9973   $227.00   $227.00   $227.00  
  Purchase #7 $90.75   10.693%   $100.4539   $100.45   $100.45   $100.50  
  7 purchase totals = $946.01       $1,035.4102   $1,035.40   $1,035.40   $1,035.50