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	$140.48	9.386%	$153.6655	$153.67	$153.65	$153.70
Purchase #2	$40.32	6.658%	$43.0045	$43.00	$43.00	$43.00
Purchase #3	$18.51	12.607%	$20.8436	$20.84	$20.85	$20.80
Purchase #4	$179.56	5.179%	$188.8594	$188.86	$188.85	$188.90
Purchase #5	$183.40	3.697%	$190.1803	$190.18	$190.20	$190.20
Purchase #6	$158.27	9.530%	$173.3531	$173.35	$173.35	$173.40
Purchase #7	$236.83	4.655%	$247.8544	$247.85	$247.85	$247.90
7 purchase totals =	$957.37		$1,017.7608	$1,017.75	$1,017.75	$1,017.90