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	$135.55	11.846%	$151.6073	$151.61	$151.60	$151.60
Purchase #2	$73.77	5.752%	$78.0133	$78.01	$78.00	$78.00
Purchase #3	$230.45	9.749%	$252.9166	$252.92	$252.90	$252.90
Purchase #4	$232.59	9.871%	$255.549	$255.55	$255.55	$255.50
Purchase #5	$100.76	4.622%	$105.4171	$105.42	$105.40	$105.40
Purchase #6	$218.48	4.399%	$228.0909	$228.09	$228.10	$228.10
Purchase #7	$137.77	11.712%	$153.9056	$153.91	$153.90	$153.90
7 purchase totals =	$1,129.37		$1,225.4998	$1,225.51	$1,225.45	$1,225.40