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 $95.99   12.461%   $107.9513   $107.95   $107.95   $108.00  
  Purchase #2 $32.77   9.806%   $35.9834   $35.98   $36.00   $36.00  
  Purchase #3 $148.35   13.530%   $168.4218   $168.42   $168.40   $168.40  
  Purchase #4 $21.70   9.593%   $23.7817   $23.78   $23.80   $23.80  
  Purchase #5 $223.70   4.582%   $233.9499   $233.95   $233.95   $233.90  
  Purchase #6 $213.44   5.503%   $225.1856   $225.19   $225.20   $225.20  
  Purchase #7 $46.60   7.408%   $50.0521   $50.05   $50.05   $50.10  
  7 purchase totals = $782.55       $845.3258   $845.32   $845.35   $845.40