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	$89.88	4.865%	$94.2527	$94.25	$94.25	$94.30
Purchase #2	$232.30	11.312%	$258.5778	$258.58	$258.60	$258.60
Purchase #3	$78.53	6.615%	$83.7248	$83.72	$83.70	$83.70
Purchase #4	$129.89	11.451%	$144.7637	$144.76	$144.75	$144.80
Purchase #5	$166.44	4.531%	$173.9814	$173.98	$174.00	$174.00
Purchase #6	$223.66	13.260%	$253.3173	$253.32	$253.30	$253.30
Purchase #7	$133.27	13.714%	$151.5466	$151.55	$151.55	$151.50
7 purchase totals =	$1,053.97		$1,160.1643	$1,160.16	$1,160.15	$1,160.20