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	$100.86	7.684%	$108.6101	$108.61	$108.60	$108.60
Purchase #2	$119.63	7.315%	$128.3809	$128.38	$128.40	$128.40
Purchase #3	$127.96	3.777%	$132.793	$132.79	$132.80	$132.80
Purchase #4	$145.25	13.754%	$165.2277	$165.23	$165.25	$165.20
Purchase #5	$102.61	8.712%	$111.5494	$111.55	$111.55	$111.50
Purchase #6	$89.80	11.297%	$99.9447	$99.94	$99.95	$99.90
Purchase #7	$224.26	9.514%	$245.5961	$245.60	$245.60	$245.60
7 purchase totals =	$910.37		$992.1019	$992.10	$992.15	$992.00