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 $151.62   7.296%   $162.6822   $162.68   $162.70   $162.70  
  Purchase #2 $235.53   4.176%   $245.3657   $245.37   $245.35   $245.40  
  Purchase #3 $100.32   5.464%   $105.8015   $105.80   $105.80   $105.80  
  Purchase #4 $220.74   6.428%   $234.9292   $234.93   $234.95   $234.90  
  Purchase #5 $61.79   5.184%   $64.9932   $64.99   $65.00   $65.00  
  Purchase #6 $242.54   5.269%   $255.3194   $255.32   $255.30   $255.30  
  Purchase #7 $83.74   6.551%   $89.2258   $89.23   $89.25   $89.20  
  7 purchase totals = $1,096.28       $1,158.3170   $1,158.32   $1,158.35   $1,158.30