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 $59.47   4.226%   $61.9832   $61.98   $62.00   $62.00  
  Purchase #2 $149.83   12.824%   $169.0442   $169.04   $169.05   $169.00  
  Purchase #3 $143.63   5.177%   $151.0657   $151.07   $151.05   $151.10  
  Purchase #4 $181.36   3.265%   $187.2814   $187.28   $187.30   $187.30  
  Purchase #5 $53.89   3.707%   $55.8877   $55.89   $55.90   $55.90  
  Purchase #6 $210.44   4.187%   $219.2511   $219.25   $219.25   $219.30  
  Purchase #7 $202.42   11.738%   $226.1801   $226.18   $226.20   $226.20  
  7 purchase totals = $1,001.04       $1,070.6934   $1,070.69   $1,070.75   $1,070.80