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 $92.81   11.634%   $103.6075   $103.61   $103.60   $103.60  
  Purchase #2 $200.77   5.834%   $212.4829   $212.48   $212.50   $212.50  
  Purchase #3 $32.64   7.220%   $34.9966   $35.00   $35.00   $35.00  
  Purchase #4 $202.26   10.591%   $223.6814   $223.68   $223.70   $223.70  
  Purchase #5 $194.46   5.224%   $204.6186   $204.62   $204.60   $204.60  
  Purchase #6 $20.65   6.375%   $21.9664   $21.97   $21.95   $22.00  
  Purchase #7 $75.76   11.711%   $84.6323   $84.63   $84.65   $84.60  
  7 purchase totals = $819.35       $885.9857   $885.99   $886.00   $886.00