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	$153.32	3.179%	$158.194	$158.19	$158.20	$158.20
Purchase #2	$41.78	11.753%	$46.6904	$46.69	$46.70	$46.70
Purchase #3	$178.78	10.109%	$196.8529	$196.85	$196.85	$196.90
Purchase #4	$231.32	9.634%	$253.6054	$253.61	$253.60	$253.60
Purchase #5	$88.79	9.392%	$97.1292	$97.13	$97.15	$97.10
Purchase #6	$35.28	9.772%	$38.7276	$38.73	$38.75	$38.70
Purchase #7	$168.90	4.335%	$176.2218	$176.22	$176.20	$176.20
7 purchase totals =	$898.17		$967.4213	$967.42	$967.45	$967.40