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	$78.62	12.572%	$88.5041	$88.50	$88.50	$88.50
Purchase #2	$195.30	13.717%	$222.0893	$222.09	$222.10	$222.10
Purchase #3	$241.95	11.116%	$268.8452	$268.85	$268.85	$268.80
Purchase #4	$230.74	9.479%	$252.6118	$252.61	$252.60	$252.60
Purchase #5	$57.28	3.796%	$59.4543	$59.45	$59.45	$59.50
Purchase #6	$223.93	9.290%	$244.7331	$244.73	$244.75	$244.70
Purchase #7	$42.81	6.737%	$45.6941	$45.69	$45.70	$45.70
7 purchase totals =	$1,070.63		$1,181.9319	$1,181.92	$1,181.95	$1,181.90