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 $46.86   12.585%   $52.7573   $52.76   $52.75   $52.80  
  Purchase #2 $34.34   4.698%   $35.9533   $35.95   $35.95   $36.00  
  Purchase #3 $170.73   9.302%   $186.6113   $186.61   $186.60   $186.60  
  Purchase #4 $205.80   4.132%   $214.3037   $214.30   $214.30   $214.30  
  Purchase #5 $183.42   9.762%   $201.3255   $201.33   $201.35   $201.30  
  Purchase #6 $223.55   9.417%   $244.6017   $244.60   $244.60   $244.60  
  Purchase #7 $140.71   8.569%   $152.7674   $152.77   $152.75   $152.80  
  7 purchase totals = $1,005.41       $1,088.3202   $1,088.32   $1,088.30   $1,088.40