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 $101.75   11.693%   $113.6476   $113.65   $113.65   $113.60  
  Purchase #2 $237.84   7.149%   $254.8432   $254.84   $254.85   $254.80  
  Purchase #3 $56.38   7.426%   $60.5668   $60.57   $60.55   $60.60  
  Purchase #4 $162.59   12.542%   $182.982   $182.98   $183.00   $183.00  
  Purchase #5 $58.29   7.532%   $62.6804   $62.68   $62.70   $62.70  
  Purchase #6 $204.69   12.584%   $230.4482   $230.45   $230.45   $230.40  
  Purchase #7 $189.97   3.734%   $197.0635   $197.06   $197.05   $197.10  
  7 purchase totals = $1,011.51       $1,102.2317   $1,102.23   $1,102.25   $1,102.20