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	$231.58	3.131%	$238.8308	$238.83	$238.85	$238.80
Purchase #2	$10.77	10.563%	$11.9076	$11.91	$11.90	$11.90
Purchase #3	$18.72	13.582%	$21.2626	$21.26	$21.25	$21.30
Purchase #4	$45.35	11.709%	$50.66	$50.66	$50.65	$50.70
Purchase #5	$30.93	11.736%	$34.5599	$34.56	$34.55	$34.60
Purchase #6	$146.47	12.611%	$164.9413	$164.94	$164.95	$164.90
Purchase #7	$158.37	3.750%	$164.3089	$164.31	$164.30	$164.30
7 purchase totals =	$642.19		$686.4711	$686.47	$686.45	$686.50