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	$234.73	3.552%	$243.0676	$243.07	$243.05	$243.10
Purchase #2	$56.61	12.319%	$63.5838	$63.58	$63.60	$63.60
Purchase #3	$57.64	11.391%	$64.2058	$64.21	$64.20	$64.20
Purchase #4	$78.88	13.301%	$89.3718	$89.37	$89.35	$89.40
Purchase #5	$165.65	12.540%	$186.4225	$186.42	$186.40	$186.40
Purchase #6	$214.51	6.383%	$228.2022	$228.20	$228.20	$228.20
Purchase #7	$173.51	10.632%	$191.9576	$191.96	$191.95	$192.00
7 purchase totals =	$981.53		$1,066.8113	$1,066.81	$1,066.75	$1,066.90