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	$29.84	8.507%	$32.3785	$32.38	$32.40	$32.40
Purchase #2	$225.42	6.646%	$240.4014	$240.40	$240.40	$240.40
Purchase #3	$226.70	12.306%	$254.5977	$254.60	$254.60	$254.60
Purchase #4	$100.49	13.117%	$113.6713	$113.67	$113.65	$113.70
Purchase #5	$117.91	8.366%	$127.7744	$127.77	$127.75	$127.80
Purchase #6	$139.61	9.749%	$153.2206	$153.22	$153.20	$153.20
Purchase #7	$212.90	4.659%	$222.819	$222.82	$222.80	$222.80
7 purchase totals =	$1,052.87		$1,144.8629	$1,144.86	$1,144.80	$1,144.90