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	$161.28	11.365%	$179.6095	$179.61	$179.60	$179.60
Purchase #2	$48.85	4.408%	$51.0033	$51.00	$51.00	$51.00
Purchase #3	$216.72	8.185%	$234.4585	$234.46	$234.45	$234.50
Purchase #4	$35.41	11.560%	$39.5034	$39.50	$39.50	$39.50
Purchase #5	$197.26	13.438%	$223.7678	$223.77	$223.75	$223.80
Purchase #6	$225.85	6.650%	$240.869	$240.87	$240.85	$240.90
Purchase #7	$105.39	5.243%	$110.9156	$110.92	$110.90	$110.90
7 purchase totals =	$990.76		$1,080.1271	$1,080.13	$1,080.05	$1,080.20