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 $82.91   13.800%   $94.3516   $94.35   $94.35   $94.40  
  Purchase #2 $234.35   10.412%   $258.7505   $258.75   $258.75   $258.80  
  Purchase #3 $89.65   3.828%   $93.0818   $93.08   $93.10   $93.10  
  Purchase #4 $208.89   3.583%   $216.3745   $216.37   $216.35   $216.40  
  Purchase #5 $126.80   4.395%   $132.3729   $132.37   $132.35   $132.40  
  Purchase #6 $133.80   13.194%   $151.4536   $151.45   $151.45   $151.50  
  Purchase #7 $95.84   3.784%   $99.4666   $99.47   $99.45   $99.50  
  7 purchase totals = $972.24       $1,045.8515   $1,045.84   $1,045.80   $1,046.10