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	$226.77	5.222%	$238.6119	$238.61	$238.60	$238.60
Purchase #2	$52.51	8.368%	$56.904	$56.90	$56.90	$56.90
Purchase #3	$126.29	12.252%	$141.7631	$141.76	$141.75	$141.80
Purchase #4	$235.93	12.223%	$264.7677	$264.77	$264.75	$264.80
Purchase #5	$250.78	6.609%	$267.3541	$267.35	$267.35	$267.40
Purchase #6	$130.65	6.832%	$139.576	$139.58	$139.60	$139.60
Purchase #7	$165.55	13.713%	$188.2519	$188.25	$188.25	$188.30
7 purchase totals =	$1,188.48		$1,297.2287	$1,297.22	$1,297.20	$1,297.40