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	$204.25	9.241%	$223.1247	$223.12	$223.10	$223.10
Purchase #2	$139.91	12.497%	$157.3946	$157.39	$157.40	$157.40
Purchase #3	$32.52	7.815%	$35.0614	$35.06	$35.05	$35.10
Purchase #4	$241.49	6.188%	$256.4334	$256.43	$256.45	$256.40
Purchase #5	$174.37	4.299%	$181.8662	$181.87	$181.85	$181.90
Purchase #6	$78.37	13.792%	$89.1788	$89.18	$89.20	$89.20
Purchase #7	$245.79	3.512%	$254.4221	$254.42	$254.40	$254.40
7 purchase totals =	$1,116.70		$1,197.4812	$1,197.47	$1,197.45	$1,197.50