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	$128.50	11.406%	$143.1567	$143.16	$143.15	$143.20
Purchase #2	$116.42	11.196%	$129.4544	$129.45	$129.45	$129.50
Purchase #3	$115.71	13.543%	$131.3806	$131.38	$131.40	$131.40
Purchase #4	$219.66	7.830%	$236.8594	$236.86	$236.85	$236.90
Purchase #5	$136.86	6.701%	$146.031	$146.03	$146.05	$146.00
Purchase #6	$59.38	7.866%	$64.0508	$64.05	$64.05	$64.10
Purchase #7	$59.88	7.345%	$64.2782	$64.28	$64.30	$64.30
7 purchase totals =	$836.41		$915.2111	$915.21	$915.25	$915.40