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 $106.98   6.748%   $114.199   $114.20   $114.20   $114.20  
  Purchase #2 $250.43   13.165%   $283.3991   $283.40   $283.40   $283.40  
  Purchase #3 $111.68   12.511%   $125.6523   $125.65   $125.65   $125.70  
  Purchase #4 $22.35   12.251%   $25.0881   $25.09   $25.10   $25.10  
  Purchase #5 $211.59   12.829%   $238.7349   $238.73   $238.75   $238.70  
  Purchase #6 $54.93   13.197%   $62.1791   $62.18   $62.20   $62.20  
  Purchase #7 $96.73   10.120%   $106.5191   $106.52   $106.50   $106.50  
  7 purchase totals = $854.69       $955.7716   $955.77   $955.80   $955.80