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	$148.73	5.232%	$156.5116	$156.51	$156.50	$156.50
Purchase #2	$165.46	11.651%	$184.7377	$184.74	$184.75	$184.70
Purchase #3	$197.28	3.835%	$204.8457	$204.85	$204.85	$204.80
Purchase #4	$80.33	12.678%	$90.5142	$90.51	$90.50	$90.50
Purchase #5	$74.44	5.171%	$78.2893	$78.29	$78.30	$78.30
Purchase #6	$192.44	6.834%	$205.5913	$205.59	$205.60	$205.60
Purchase #7	$227.63	10.489%	$251.5061	$251.51	$251.50	$251.50
7 purchase totals =	$1,086.31		$1,171.9959	$1,172.00	$1,172.00	$1,171.90