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 $84.56   13.474%   $95.9536   $95.95   $95.95   $96.00  
  Purchase #2 $110.71   10.755%   $122.6169   $122.62   $122.60   $122.60  
  Purchase #3 $64.37   11.490%   $71.7661   $71.77   $71.75   $71.80  
  Purchase #4 $241.67   8.840%   $263.0336   $263.03   $263.05   $263.00  
  Purchase #5 $159.38   4.733%   $166.9235   $166.92   $166.90   $166.90  
  Purchase #6 $107.50   9.367%   $117.5695   $117.57   $117.55   $117.60  
  Purchase #7 $239.27   12.319%   $268.7457   $268.75   $268.75   $268.70  
  7 purchase totals = $1,007.46       $1,106.6089   $1,106.61   $1,106.55   $1,106.60