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	$107.91	3.361%	$111.5369	$111.54	$111.55	$111.50
Purchase #2	$55.82	13.378%	$63.2876	$63.29	$63.30	$63.30
Purchase #3	$74.58	8.137%	$80.6486	$80.65	$80.65	$80.60
Purchase #4	$232.29	13.121%	$262.7688	$262.77	$262.75	$262.80
Purchase #5	$76.59	10.180%	$84.3869	$84.39	$84.40	$84.40
Purchase #6	$39.56	5.466%	$41.7223	$41.72	$41.70	$41.70
Purchase #7	$140.56	8.494%	$152.4992	$152.50	$152.50	$152.50
7 purchase totals =	$727.31		$796.8503	$796.86	$796.85	$796.80