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	$184.52	13.413%	$209.2697	$209.27	$209.25	$209.30
Purchase #2	$29.89	9.782%	$32.8138	$32.81	$32.80	$32.80
Purchase #3	$237.91	12.168%	$266.8589	$266.86	$266.85	$266.90
Purchase #4	$149.53	4.102%	$155.6637	$155.66	$155.65	$155.70
Purchase #5	$204.42	12.104%	$229.163	$229.16	$229.15	$229.20
Purchase #6	$127.62	12.437%	$143.4921	$143.49	$143.50	$143.50
Purchase #7	$162.97	3.314%	$168.3708	$168.37	$168.35	$168.40
7 purchase totals =	$1,096.86		$1,205.6320	$1,205.62	$1,205.55	$1,205.80