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 $195.48   12.168%   $219.266   $219.27   $219.25   $219.30  
  Purchase #2 $219.95   11.230%   $244.6504   $244.65   $244.65   $244.70  
  Purchase #3 $153.96   12.279%   $172.8647   $172.86   $172.85   $172.90  
  Purchase #4 $159.26   11.420%   $177.4475   $177.45   $177.45   $177.40  
  Purchase #5 $183.37   10.553%   $202.721   $202.72   $202.70   $202.70  
  Purchase #6 $117.33   6.545%   $125.0092   $125.01   $125.00   $125.00  
  Purchase #7 $57.53   4.355%   $60.0354   $60.04   $60.05   $60.00  
  7 purchase totals = $1,086.88       $1,201.9942   $1,202.00   $1,201.95   $1,202.00