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	$61.50	4.224%	$64.0978	$64.10	$64.10	$64.10
Purchase #2	$83.37	8.524%	$90.4765	$90.48	$90.50	$90.50
Purchase #3	$146.36	3.591%	$151.6158	$151.62	$151.60	$151.60
Purchase #4	$104.42	3.485%	$108.059	$108.06	$108.05	$108.10
Purchase #5	$47.49	12.337%	$53.3488	$53.35	$53.35	$53.30
Purchase #6	$224.68	12.785%	$253.4053	$253.41	$253.40	$253.40
Purchase #7	$12.27	8.648%	$13.3311	$13.33	$13.35	$13.30
7 purchase totals =	$680.09		$734.3343	$734.35	$734.35	$734.30