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	$59.26	3.433%	$61.2944	$61.29	$61.30	$61.30
Purchase #2	$81.74	4.123%	$85.1101	$85.11	$85.10	$85.10
Purchase #3	$159.69	4.382%	$166.6876	$166.69	$166.70	$166.70
Purchase #4	$224.82	10.608%	$248.6689	$248.67	$248.65	$248.70
Purchase #5	$186.40	7.775%	$200.8926	$200.89	$200.90	$200.90
Purchase #6	$133.98	7.403%	$143.8985	$143.90	$143.90	$143.90
Purchase #7	$157.31	9.486%	$172.2324	$172.23	$172.25	$172.20
7 purchase totals =	$1,003.20		$1,078.7845	$1,078.78	$1,078.80	$1,078.80