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	$212.42	3.715%	$220.3114	$220.31	$220.30	$220.30
Purchase #2	$92.48	3.154%	$95.3968	$95.40	$95.40	$95.40
Purchase #3	$61.90	13.370%	$70.176	$70.18	$70.20	$70.20
Purchase #4	$126.61	3.205%	$130.6679	$130.67	$130.65	$130.70
Purchase #5	$131.48	8.868%	$143.1396	$143.14	$143.15	$143.10
Purchase #6	$98.58	11.489%	$109.9059	$109.91	$109.90	$109.90
Purchase #7	$160.62	7.617%	$172.8544	$172.85	$172.85	$172.90
7 purchase totals =	$884.09		$942.4520	$942.46	$942.45	$942.50