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	$223.62	8.172%	$241.8942	$241.89	$241.90	$241.90
Purchase #2	$124.56	11.727%	$139.1672	$139.17	$139.15	$139.20
Purchase #3	$149.43	10.722%	$165.4519	$165.45	$165.45	$165.50
Purchase #4	$175.68	9.241%	$191.9146	$191.91	$191.90	$191.90
Purchase #5	$88.46	3.776%	$91.8002	$91.80	$91.80	$91.80
Purchase #6	$244.74	11.837%	$273.7099	$273.71	$273.70	$273.70
Purchase #7	$165.92	12.371%	$186.446	$186.45	$186.45	$186.40
7 purchase totals =	$1,172.41		$1,290.3840	$1,290.38	$1,290.35	$1,290.40