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 $91.25   3.226%   $94.1937   $94.19   $94.20   $94.20  
  Purchase #2 $113.53   11.160%   $126.1999   $126.20   $126.20   $126.20  
  Purchase #3 $245.59   3.153%   $253.3335   $253.33   $253.35   $253.30  
  Purchase #4 $189.88   9.193%   $207.3357   $207.34   $207.35   $207.30  
  Purchase #5 $174.67   7.759%   $188.2226   $188.22   $188.20   $188.20  
  Purchase #6 $48.27   3.845%   $50.126   $50.13   $50.15   $50.10  
  Purchase #7 $188.86   4.116%   $196.6335   $196.63   $196.65   $196.60  
  7 purchase totals = $1,052.05       $1,116.0449   $1,116.04   $1,116.10   $1,115.90