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	$98.34	4.310%	$102.5785	$102.58	$102.60	$102.60
Purchase #2	$187.32	7.278%	$200.9531	$200.95	$200.95	$201.00
Purchase #3	$70.94	12.312%	$79.6741	$79.67	$79.65	$79.70
Purchase #4	$173.73	13.149%	$196.5738	$196.57	$196.55	$196.60
Purchase #5	$57.84	13.192%	$65.4703	$65.47	$65.45	$65.50
Purchase #6	$165.95	13.659%	$188.6171	$188.62	$188.60	$188.60
Purchase #7	$19.83	8.702%	$21.5556	$21.56	$21.55	$21.60
7 purchase totals =	$773.95		$855.4225	$855.42	$855.35	$855.60