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	$53.53	12.551%	$60.2486	$60.25	$60.25	$60.20
Purchase #2	$228.97	9.541%	$250.816	$250.82	$250.80	$250.80
Purchase #3	$108.81	10.684%	$120.4353	$120.44	$120.45	$120.40
Purchase #4	$145.66	4.737%	$152.5599	$152.56	$152.55	$152.60
Purchase #5	$238.72	10.233%	$263.1482	$263.15	$263.15	$263.10
Purchase #6	$54.73	5.378%	$57.6734	$57.67	$57.65	$57.70
Purchase #7	$243.36	4.304%	$253.8342	$253.83	$253.85	$253.80
7 purchase totals =	$1,073.78		$1,158.7156	$1,158.72	$1,158.70	$1,158.60