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	$179.90	3.765%	$186.6732	$186.67	$186.65	$186.70
Purchase #2	$177.43	8.153%	$191.8959	$191.90	$191.90	$191.90
Purchase #3	$123.56	5.255%	$130.0531	$130.05	$130.05	$130.10
Purchase #4	$32.98	13.137%	$37.3126	$37.31	$37.30	$37.30
Purchase #5	$145.40	8.363%	$157.5598	$157.56	$157.55	$157.60
Purchase #6	$167.36	3.443%	$173.1222	$173.12	$173.10	$173.10
Purchase #7	$109.69	7.726%	$118.1646	$118.16	$118.15	$118.20
7 purchase totals =	$936.32		$994.7814	$994.77	$994.70	$994.90