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	$151.80	8.790%	$165.1432	$165.14	$165.15	$165.10
Purchase #2	$13.41	9.163%	$14.6388	$14.64	$14.65	$14.60
Purchase #3	$42.32	4.389%	$44.1774	$44.18	$44.20	$44.20
Purchase #4	$200.40	10.801%	$222.0452	$222.05	$222.05	$222.00
Purchase #5	$79.98	13.338%	$90.6477	$90.65	$90.65	$90.60
Purchase #6	$55.51	9.127%	$60.5764	$60.58	$60.60	$60.60
Purchase #7	$125.44	9.251%	$137.0445	$137.04	$137.05	$137.00
7 purchase totals =	$668.86		$734.2732	$734.28	$734.35	$734.10