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	$193.55	11.738%	$216.2689	$216.27	$216.25	$216.30
Purchase #2	$239.80	10.118%	$264.063	$264.06	$264.05	$264.10
Purchase #3	$142.62	6.286%	$151.5851	$151.59	$151.60	$151.60
Purchase #4	$213.32	12.675%	$240.3583	$240.36	$240.35	$240.40
Purchase #5	$198.59	3.488%	$205.5168	$205.52	$205.50	$205.50
Purchase #6	$120.88	5.750%	$127.8306	$127.83	$127.85	$127.80
Purchase #7	$138.36	6.585%	$147.471	$147.47	$147.45	$147.50
7 purchase totals =	$1,247.12		$1,353.0937	$1,353.10	$1,353.05	$1,353.20