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	$222.63	4.411%	$232.4502	$232.45	$232.45	$232.50
Purchase #2	$58.56	5.344%	$61.6894	$61.69	$61.70	$61.70
Purchase #3	$65.51	10.170%	$72.1724	$72.17	$72.15	$72.20
Purchase #4	$233.29	10.717%	$258.2917	$258.29	$258.30	$258.30
Purchase #5	$240.32	7.471%	$258.2743	$258.27	$258.25	$258.30
Purchase #6	$59.96	6.820%	$64.0493	$64.05	$64.05	$64.00
Purchase #7	$132.73	5.847%	$140.4907	$140.49	$140.50	$140.50
7 purchase totals =	$1,013.00		$1,087.4180	$1,087.41	$1,087.40	$1,087.50