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	$144.87	10.173%	$159.6076	$159.61	$159.60	$159.60
Purchase #2	$214.78	4.360%	$224.1444	$224.14	$224.15	$224.10
Purchase #3	$72.27	7.852%	$77.9446	$77.94	$77.95	$77.90
Purchase #4	$174.64	4.816%	$183.0507	$183.05	$183.05	$183.10
Purchase #5	$73.69	10.476%	$81.4098	$81.41	$81.40	$81.40
Purchase #6	$165.30	10.560%	$182.7557	$182.76	$182.75	$182.80
Purchase #7	$103.72	6.633%	$110.5997	$110.60	$110.60	$110.60
7 purchase totals =	$949.27		$1,019.5125	$1,019.51	$1,019.50	$1,019.50