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	$164.54	7.536%	$176.9397	$176.94	$176.95	$176.90
Purchase #2	$40.70	11.216%	$45.2649	$45.26	$45.25	$45.30
Purchase #3	$123.43	3.144%	$127.3106	$127.31	$127.30	$127.30
Purchase #4	$106.50	10.330%	$117.5015	$117.50	$117.50	$117.50
Purchase #5	$243.27	10.669%	$269.2245	$269.22	$269.20	$269.20
Purchase #6	$184.77	3.162%	$190.6124	$190.61	$190.60	$190.60
Purchase #7	$128.63	13.672%	$146.2163	$146.22	$146.20	$146.20
7 purchase totals =	$991.84		$1,073.0699	$1,073.06	$1,073.00	$1,073.00