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	$146.89	3.300%	$151.7374	$151.74	$151.75	$151.70
Purchase #2	$165.27	4.463%	$172.646	$172.65	$172.65	$172.60
Purchase #3	$208.50	7.136%	$223.3786	$223.38	$223.40	$223.40
Purchase #4	$207.31	5.456%	$218.6208	$218.62	$218.60	$218.60
Purchase #5	$217.62	9.397%	$238.0698	$238.07	$238.05	$238.10
Purchase #6	$6.42	13.653%	$7.2965	$7.30	$7.30	$7.30
Purchase #7	$108.38	13.819%	$123.357	$123.36	$123.35	$123.40
7 purchase totals =	$1,060.39		$1,135.1061	$1,135.12	$1,135.10	$1,135.10