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	$131.77	7.306%	$141.3971	$141.40	$141.40	$141.40
Purchase #2	$98.45	7.125%	$105.4646	$105.46	$105.45	$105.50
Purchase #3	$96.81	8.413%	$104.9546	$104.95	$104.95	$105.00
Purchase #4	$10.88	12.868%	$12.28	$12.28	$12.30	$12.30
Purchase #5	$194.51	7.606%	$209.3044	$209.30	$209.30	$209.30
Purchase #6	$66.95	11.399%	$74.5816	$74.58	$74.60	$74.60
Purchase #7	$50.66	13.335%	$57.4155	$57.42	$57.40	$57.40
7 purchase totals =	$650.03		$705.3978	$705.39	$705.40	$705.50