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 $208.83   11.653%   $233.165   $233.17   $233.15   $233.20  
  Purchase #2 $75.81   9.551%   $83.0506   $83.05   $83.05   $83.10  
  Purchase #3 $120.98   9.725%   $132.7453   $132.75   $132.75   $132.70  
  Purchase #4 $32.64   7.232%   $35.0005   $35.00   $35.00   $35.00  
  Purchase #5 $5.38   13.340%   $6.0977   $6.10   $6.10   $6.10  
  Purchase #6 $198.59   11.374%   $221.1776   $221.18   $221.20   $221.20  
  Purchase #7 $212.45   9.838%   $233.3508   $233.35   $233.35   $233.40  
  7 purchase totals = $854.68       $944.5875   $944.60   $944.60   $944.70