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	$141.30	5.263%	$148.7366	$148.74	$148.75	$148.70
Purchase #2	$146.60	5.830%	$155.1468	$155.15	$155.15	$155.10
Purchase #3	$187.55	12.530%	$211.05	$211.05	$211.05	$211.10
Purchase #4	$165.87	13.585%	$188.4034	$188.40	$188.40	$188.40
Purchase #5	$67.50	5.760%	$71.388	$71.39	$71.40	$71.40
Purchase #6	$131.59	7.537%	$141.5079	$141.51	$141.50	$141.50
Purchase #7	$147.94	7.465%	$158.9837	$158.98	$159.00	$159.00
7 purchase totals =	$988.35		$1,075.2164	$1,075.22	$1,075.25	$1,075.20