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	$78.52	8.610%	$85.2806	$85.28	$85.30	$85.30
Purchase #2	$153.80	13.112%	$173.9663	$173.97	$173.95	$174.00
Purchase #3	$43.27	3.203%	$44.6559	$44.66	$44.65	$44.70
Purchase #4	$159.98	3.453%	$165.5041	$165.50	$165.50	$165.50
Purchase #5	$180.72	6.267%	$192.0457	$192.05	$192.05	$192.00
Purchase #6	$197.67	13.244%	$223.8494	$223.85	$223.85	$223.80
Purchase #7	$46.64	13.859%	$53.1038	$53.10	$53.10	$53.10
7 purchase totals =	$860.60		$938.4058	$938.41	$938.40	$938.40