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	$70.96	7.247%	$76.1025	$76.10	$76.10	$76.10
Purchase #2	$7.72	4.177%	$8.0425	$8.04	$8.05	$8.00
Purchase #3	$156.66	12.168%	$175.7224	$175.72	$175.70	$175.70
Purchase #4	$72.39	6.777%	$77.2959	$77.30	$77.30	$77.30
Purchase #5	$28.76	12.827%	$32.449	$32.45	$32.45	$32.40
Purchase #6	$70.39	11.537%	$78.5109	$78.51	$78.50	$78.50
Purchase #7	$153.96	12.787%	$173.6469	$173.65	$173.65	$173.60
7 purchase totals =	$560.84		$621.7701	$621.77	$621.75	$621.60