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	$33.26	4.594%	$34.788	$34.79	$34.80	$34.80
Purchase #2	$69.68	4.663%	$72.9292	$72.93	$72.95	$72.90
Purchase #3	$91.52	8.596%	$99.3871	$99.39	$99.40	$99.40
Purchase #4	$141.38	12.571%	$159.1529	$159.15	$159.15	$159.20
Purchase #5	$84.39	13.286%	$95.6021	$95.60	$95.60	$95.60
Purchase #6	$146.89	9.259%	$160.4905	$160.49	$160.50	$160.50
Purchase #7	$124.71	9.425%	$136.4639	$136.46	$136.45	$136.50
7 purchase totals =	$691.83		$758.8137	$758.81	$758.85	$758.90