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 $103.93   8.306%   $112.5624   $112.56   $112.55   $112.60  
  Purchase #2 $249.45   10.545%   $275.7545   $275.75   $275.75   $275.80  
  Purchase #3 $169.35   11.211%   $188.3358   $188.34   $188.35   $188.30  
  Purchase #4 $57.75   7.524%   $62.0951   $62.10   $62.10   $62.10  
  Purchase #5 $109.90   5.111%   $115.517   $115.52   $115.50   $115.50  
  Purchase #6 $18.41   4.713%   $19.2777   $19.28   $19.30   $19.30  
  Purchase #7 $224.29   7.354%   $240.7843   $240.78   $240.80   $240.80  
  7 purchase totals = $933.08       $1,014.3268   $1,014.33   $1,014.35   $1,014.40