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 $23.38   11.352%   $26.0341   $26.03   $26.05   $26.00  
  Purchase #2 $176.87   9.562%   $193.7823   $193.78   $193.80   $193.80  
  Purchase #3 $223.85   7.251%   $240.0814   $240.08   $240.10   $240.10  
  Purchase #4 $54.39   13.597%   $61.7854   $61.79   $61.80   $61.80  
  Purchase #5 $250.68   5.829%   $265.2921   $265.29   $265.30   $265.30  
  Purchase #6 $32.59   12.389%   $36.6276   $36.63   $36.65   $36.60  
  Purchase #7 $223.75   6.288%   $237.8194   $237.82   $237.80   $237.80  
  7 purchase totals = $985.51       $1,061.4223   $1,061.42   $1,061.50   $1,061.40