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 $112.96   11.716%   $126.1944   $126.19   $126.20   $126.20  
  Purchase #2 $223.55   5.501%   $235.8475   $235.85   $235.85   $235.80  
  Purchase #3 $107.84   9.663%   $118.2606   $118.26   $118.25   $118.30  
  Purchase #4 $87.29   10.701%   $96.6309   $96.63   $96.65   $96.60  
  Purchase #5 $13.65   8.218%   $14.7718   $14.77   $14.75   $14.80  
  Purchase #6 $219.85   9.723%   $241.226   $241.23   $241.25   $241.20  
  Purchase #7 $110.90   3.789%   $115.102   $115.10   $115.10   $115.10  
  7 purchase totals = $876.04       $948.0332   $948.03   $948.05   $948.00