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	$238.53	6.675%	$254.4519	$254.45	$254.45	$254.50
Purchase #2	$158.55	10.324%	$174.9187	$174.92	$174.90	$174.90
Purchase #3	$49.70	11.389%	$55.3603	$55.36	$55.35	$55.40
Purchase #4	$153.90	9.561%	$168.6144	$168.61	$168.60	$168.60
Purchase #5	$63.97	10.423%	$70.6376	$70.64	$70.65	$70.60
Purchase #6	$56.38	6.636%	$60.1214	$60.12	$60.10	$60.10
Purchase #7	$210.51	13.405%	$238.7289	$238.73	$238.75	$238.70
7 purchase totals =	$931.54		$1,022.8332	$1,022.83	$1,022.80	$1,022.80