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	$94.67	13.806%	$107.7401	$107.74	$107.75	$107.70
Purchase #2	$69.52	10.353%	$76.7174	$76.72	$76.70	$76.70
Purchase #3	$50.97	4.224%	$53.123	$53.12	$53.10	$53.10
Purchase #4	$71.73	12.250%	$80.5169	$80.52	$80.50	$80.50
Purchase #5	$97.46	5.846%	$103.1575	$103.16	$103.15	$103.20
Purchase #6	$141.28	13.546%	$160.4178	$160.42	$160.40	$160.40
Purchase #7	$66.89	8.603%	$72.6445	$72.64	$72.65	$72.60
7 purchase totals =	$592.52		$654.3172	$654.32	$654.25	$654.20