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 $92.58   9.110%   $101.014   $101.01   $101.00   $101.00  
  Purchase #2 $239.61   13.550%   $272.0772   $272.08   $272.10   $272.10  
  Purchase #3 $64.78   8.367%   $70.2001   $70.20   $70.20   $70.20  
  Purchase #4 $157.47   7.354%   $169.0503   $169.05   $169.05   $169.10  
  Purchase #5 $151.34   13.279%   $171.4364   $171.44   $171.45   $171.40  
  Purchase #6 $200.25   6.818%   $213.903   $213.90   $213.90   $213.90  
  Purchase #7 $131.62   13.604%   $149.5256   $149.53   $149.55   $149.50  
  7 purchase totals = $1,037.65       $1,147.2066   $1,147.21   $1,147.25   $1,147.20