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 $201.67   6.575%   $214.9298   $214.93   $214.95   $214.90  
  Purchase #2 $231.97   5.185%   $243.9976   $244.00   $244.00   $244.00  
  Purchase #3 $63.69   7.471%   $68.4483   $68.45   $68.45   $68.40  
  Purchase #4 $128.60   5.179%   $135.2602   $135.26   $135.25   $135.30  
  Purchase #5 $205.30   5.140%   $215.8524   $215.85   $215.85   $215.90  
  Purchase #6 $192.85   13.871%   $219.6002   $219.60   $219.60   $219.60  
  Purchase #7 $20.85   4.638%   $21.817   $21.82   $21.80   $21.80  
  7 purchase totals = $1,044.93       $1,119.9055   $1,119.91   $1,119.90   $1,119.90