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 $162.86   13.467%   $184.7924   $184.79   $184.80   $184.80  
  Purchase #2 $91.82   6.316%   $97.6194   $97.62   $97.60   $97.60  
  Purchase #3 $95.75   13.435%   $108.614   $108.61   $108.60   $108.60  
  Purchase #4 $150.81   13.232%   $170.7652   $170.77   $170.75   $170.80  
  Purchase #5 $30.28   10.164%   $33.3577   $33.36   $33.35   $33.40  
  Purchase #6 $184.83   8.739%   $200.9823   $200.98   $201.00   $201.00  
  Purchase #7 $46.75   11.390%   $52.0748   $52.07   $52.05   $52.10  
  7 purchase totals = $763.10       $848.2058   $848.20   $848.15   $848.30