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	$166.93	13.368%	$189.2452	$189.25	$189.25	$189.20
Purchase #2	$219.84	5.468%	$231.8609	$231.86	$231.85	$231.90
Purchase #3	$105.76	11.830%	$118.2714	$118.27	$118.25	$118.30
Purchase #4	$41.28	4.583%	$43.1719	$43.17	$43.15	$43.20
Purchase #5	$209.83	10.849%	$232.5945	$232.59	$232.60	$232.60
Purchase #6	$159.94	13.425%	$181.4119	$181.41	$181.40	$181.40
Purchase #7	$91.82	10.437%	$101.4033	$101.40	$101.40	$101.40
7 purchase totals =	$995.40		$1,097.9591	$1,097.95	$1,097.90	$1,098.00