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	$146.76	12.763%	$165.491	$165.49	$165.50	$165.50
Purchase #2	$227.93	7.175%	$244.284	$244.28	$244.30	$244.30
Purchase #3	$80.26	10.705%	$88.8518	$88.85	$88.85	$88.90
Purchase #4	$119.60	6.437%	$127.2987	$127.30	$127.30	$127.30
Purchase #5	$92.43	12.834%	$104.2925	$104.29	$104.30	$104.30
Purchase #6	$30.54	5.844%	$32.3248	$32.32	$32.30	$32.30
Purchase #7	$155.66	4.213%	$162.218	$162.22	$162.20	$162.20
7 purchase totals =	$853.18		$924.7608	$924.75	$924.75	$924.80