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	$77.62	13.238%	$87.8953	$87.90	$87.90	$87.90
Purchase #2	$185.29	10.400%	$204.5602	$204.56	$204.55	$204.60
Purchase #3	$112.36	13.544%	$127.578	$127.58	$127.60	$127.60
Purchase #4	$12.71	8.623%	$13.806	$13.81	$13.80	$13.80
Purchase #5	$95.61	4.448%	$99.8627	$99.86	$99.85	$99.90
Purchase #6	$229.69	10.703%	$254.2737	$254.27	$254.25	$254.30
Purchase #7	$228.68	8.236%	$247.5141	$247.51	$247.50	$247.50
7 purchase totals =	$941.96		$1,035.4900	$1,035.49	$1,035.45	$1,035.60