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 $37.88   13.548%   $43.012   $43.01   $43.00   $43.00  
  Purchase #2 $189.37   11.232%   $210.64   $210.64   $210.65   $210.60  
  Purchase #3 $79.86   5.244%   $84.0479   $84.05   $84.05   $84.00  
  Purchase #4 $216.39   9.704%   $237.3885   $237.39   $237.40   $237.40  
  Purchase #5 $52.36   7.172%   $56.1153   $56.12   $56.10   $56.10  
  Purchase #6 $206.97   3.160%   $213.5103   $213.51   $213.50   $213.50  
  Purchase #7 $22.37   3.820%   $23.2245   $23.22   $23.20   $23.20  
  7 purchase totals = $805.20       $867.9385   $867.94   $867.90   $867.80