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	$67.67	7.523%	$72.7608	$72.76	$72.75	$72.80
Purchase #2	$139.91	3.372%	$144.6278	$144.63	$144.65	$144.60
Purchase #3	$105.28	7.195%	$112.8549	$112.85	$112.85	$112.90
Purchase #4	$235.53	8.105%	$254.6197	$254.62	$254.60	$254.60
Purchase #5	$124.32	11.278%	$138.3408	$138.34	$138.35	$138.30
Purchase #6	$169.64	12.518%	$190.8755	$190.88	$190.90	$190.90
Purchase #7	$147.52	4.414%	$154.0315	$154.03	$154.05	$154.00
7 purchase totals =	$989.87		$1,068.1110	$1,068.11	$1,068.15	$1,068.10