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	$136.54	9.493%	$149.5017	$149.50	$149.50	$149.50
Purchase #2	$187.40	12.296%	$210.4427	$210.44	$210.45	$210.40
Purchase #3	$96.41	13.431%	$109.3588	$109.36	$109.35	$109.40
Purchase #4	$36.89	8.638%	$40.0766	$40.08	$40.10	$40.10
Purchase #5	$247.67	13.815%	$281.8856	$281.89	$281.90	$281.90
Purchase #6	$234.66	3.548%	$242.9857	$242.99	$243.00	$243.00
Purchase #7	$152.43	6.307%	$162.0438	$162.04	$162.05	$162.00
7 purchase totals =	$1,092.00		$1,196.2949	$1,196.30	$1,196.35	$1,196.30