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 $193.63   5.736%   $204.7366   $204.74   $204.75   $204.70  
  Purchase #2 $174.80   13.702%   $198.7511   $198.75   $198.75   $198.80  
  Purchase #3 $57.29   10.677%   $63.4069   $63.41   $63.40   $63.40  
  Purchase #4 $153.58   9.540%   $168.2315   $168.23   $168.25   $168.20  
  Purchase #5 $92.25   5.770%   $97.5728   $97.57   $97.55   $97.60  
  Purchase #6 $52.98   5.570%   $55.931   $55.93   $55.95   $55.90  
  Purchase #7 $97.45   9.590%   $106.7955   $106.80   $106.80   $106.80  
  7 purchase totals = $821.98       $895.4254   $895.43   $895.45   $895.40