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 $164.25   12.496%   $184.7747   $184.77   $184.75   $184.80  
  Purchase #2 $198.58   9.389%   $217.2247   $217.22   $217.20   $217.20  
  Purchase #3 $21.48   11.647%   $23.9818   $23.98   $24.00   $24.00  
  Purchase #4 $48.45   8.141%   $52.3943   $52.39   $52.40   $52.40  
  Purchase #5 $194.65   10.319%   $214.7359   $214.74   $214.75   $214.70  
  Purchase #6 $246.53   4.742%   $258.2205   $258.22   $258.20   $258.20  
  Purchase #7 $198.57   3.566%   $205.651   $205.65   $205.65   $205.70  
  7 purchase totals = $1,072.51       $1,156.9829   $1,156.97   $1,156.95   $1,157.00