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	$133.28	7.474%	$143.2413	$143.24	$143.25	$143.20
Purchase #2	$90.88	10.289%	$100.2306	$100.23	$100.25	$100.20
Purchase #3	$174.49	10.467%	$192.7539	$192.75	$192.75	$192.80
Purchase #4	$168.91	13.233%	$191.2619	$191.26	$191.25	$191.30
Purchase #5	$111.69	13.816%	$127.1211	$127.12	$127.10	$127.10
Purchase #6	$131.69	4.861%	$138.0915	$138.09	$138.10	$138.10
Purchase #7	$130.35	10.473%	$144.0016	$144.00	$144.00	$144.00
7 purchase totals =	$941.29		$1,036.7019	$1,036.69	$1,036.70	$1,036.70