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	$173.31	13.158%	$196.1141	$196.11	$196.10	$196.10
Purchase #2	$180.76	7.150%	$193.6843	$193.68	$193.70	$193.70
Purchase #3	$210.94	12.631%	$237.5838	$237.58	$237.60	$237.60
Purchase #4	$99.54	12.401%	$111.884	$111.88	$111.90	$111.90
Purchase #5	$168.40	11.717%	$188.1314	$188.13	$188.15	$188.10
Purchase #6	$54.49	9.228%	$59.5183	$59.52	$59.50	$59.50
Purchase #7	$124.52	12.194%	$139.704	$139.70	$139.70	$139.70
7 purchase totals =	$1,011.96		$1,126.6199	$1,126.60	$1,126.65	$1,126.60