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	$120.76	7.199%	$129.4535	$129.45	$129.45	$129.50
Purchase #2	$96.31	4.635%	$100.774	$100.77	$100.75	$100.80
Purchase #3	$142.25	12.143%	$159.5234	$159.52	$159.50	$159.50
Purchase #4	$130.40	10.811%	$144.4975	$144.50	$144.50	$144.50
Purchase #5	$101.69	13.785%	$115.708	$115.71	$115.70	$115.70
Purchase #6	$108.61	9.300%	$118.7107	$118.71	$118.70	$118.70
Purchase #7	$238.59	5.240%	$251.0921	$251.09	$251.10	$251.10
7 purchase totals =	$938.61		$1,019.7592	$1,019.75	$1,019.70	$1,019.80