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	$19.33	4.666%	$20.2319	$20.23	$20.25	$20.20
Purchase #2	$157.56	13.425%	$178.7124	$178.71	$178.70	$178.70
Purchase #3	$19.52	4.542%	$20.4066	$20.41	$20.40	$20.40
Purchase #4	$241.95	6.472%	$257.609	$257.61	$257.60	$257.60
Purchase #5	$88.63	13.255%	$100.3779	$100.38	$100.40	$100.40
Purchase #6	$80.58	7.582%	$86.6896	$86.69	$86.70	$86.70
Purchase #7	$137.70	10.185%	$151.7247	$151.72	$151.70	$151.70
7 purchase totals =	$745.27		$815.7521	$815.75	$815.75	$815.70