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	$188.90	4.174%	$196.7847	$196.78	$196.80	$196.80
Purchase #2	$81.35	11.557%	$90.7516	$90.75	$90.75	$90.80
Purchase #3	$146.97	6.461%	$156.4657	$156.47	$156.45	$156.50
Purchase #4	$237.74	13.384%	$269.5591	$269.56	$269.55	$269.60
Purchase #5	$101.88	4.732%	$106.701	$106.70	$106.70	$106.70
Purchase #6	$15.72	11.569%	$17.5386	$17.54	$17.55	$17.50
Purchase #7	$68.82	10.668%	$76.1617	$76.16	$76.15	$76.20
7 purchase totals =	$841.38		$913.9624	$913.96	$913.95	$914.10