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	$178.94	8.805%	$194.6957	$194.70	$194.70	$194.70
Purchase #2	$194.61	7.674%	$209.5444	$209.54	$209.55	$209.50
Purchase #3	$116.33	9.602%	$127.5	$127.50	$127.50	$127.50
Purchase #4	$89.37	13.670%	$101.5869	$101.59	$101.60	$101.60
Purchase #5	$145.31	6.843%	$155.2536	$155.25	$155.25	$155.30
Purchase #6	$177.27	8.384%	$192.1323	$192.13	$192.15	$192.10
Purchase #7	$104.96	11.644%	$117.1815	$117.18	$117.20	$117.20
7 purchase totals =	$1,006.79		$1,097.8944	$1,097.89	$1,097.95	$1,097.90