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 $96.89   5.118%   $101.8488   $101.85   $101.85   $101.80  
  Purchase #2 $239.86   7.629%   $258.1589   $258.16   $258.15   $258.20  
  Purchase #3 $73.84   11.433%   $82.2821   $82.28   $82.30   $82.30  
  Purchase #4 $195.29   8.435%   $211.7627   $211.76   $211.75   $211.80  
  Purchase #5 $178.68   13.474%   $202.7553   $202.76   $202.75   $202.80  
  Purchase #6 $154.90   9.164%   $169.095   $169.10   $169.10   $169.10  
  Purchase #7 $209.39   12.151%   $234.833   $234.83   $234.85   $234.80  
  7 purchase totals = $1,148.85       $1,260.7358   $1,260.74   $1,260.75   $1,260.80