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 $188.75   3.612%   $195.5677   $195.57   $195.55   $195.60  
  Purchase #2 $250.29   4.147%   $260.6695   $260.67   $260.65   $260.70  
  Purchase #3 $224.66   8.590%   $243.9583   $243.96   $243.95   $244.00  
  Purchase #4 $165.42   6.668%   $176.4502   $176.45   $176.45   $176.50  
  Purchase #5 $186.98   9.862%   $205.42   $205.42   $205.40   $205.40  
  Purchase #6 $176.88   9.251%   $193.2432   $193.24   $193.25   $193.20  
  Purchase #7 $26.93   7.145%   $28.8541   $28.85   $28.85   $28.90  
  7 purchase totals = $1,219.91       $1,304.1630   $1,304.16   $1,304.10   $1,304.30