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	$103.91	7.127%	$111.3157	$111.32	$111.30	$111.30
Purchase #2	$130.53	10.859%	$144.7043	$144.70	$144.70	$144.70
Purchase #3	$139.52	6.867%	$149.1008	$149.10	$149.10	$149.10
Purchase #4	$50.74	12.165%	$56.9125	$56.91	$56.90	$56.90
Purchase #5	$98.72	13.267%	$111.8172	$111.82	$111.80	$111.80
Purchase #6	$24.63	13.778%	$28.0235	$28.02	$28.00	$28.00
Purchase #7	$123.56	8.156%	$133.6376	$133.64	$133.65	$133.60
7 purchase totals =	$671.61		$735.5116	$735.51	$735.45	$735.40