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 $88.87   7.200%   $95.2686   $95.27   $95.25   $95.30  
  Purchase #2 $194.38   7.164%   $208.3054   $208.31   $208.30   $208.30  
  Purchase #3 $174.61   4.377%   $182.2527   $182.25   $182.25   $182.30  
  Purchase #4 $70.33   6.114%   $74.63   $74.63   $74.65   $74.60  
  Purchase #5 $179.83   13.503%   $204.1124   $204.11   $204.10   $204.10  
  Purchase #6 $143.40   8.638%   $155.7869   $155.79   $155.80   $155.80  
  Purchase #7 $211.79   12.355%   $237.9567   $237.96   $237.95   $238.00  
  7 purchase totals = $1,063.21       $1,158.3127   $1,158.32   $1,158.30   $1,158.40