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	$42.72	9.228%	$46.6622	$46.66	$46.65	$46.70
Purchase #2	$78.92	6.229%	$83.8359	$83.84	$83.85	$83.80
Purchase #3	$215.72	4.561%	$225.559	$225.56	$225.55	$225.60
Purchase #4	$202.78	3.693%	$210.2687	$210.27	$210.25	$210.30
Purchase #5	$248.77	4.522%	$260.0194	$260.02	$260.00	$260.00
Purchase #6	$248.31	5.669%	$262.3867	$262.39	$262.40	$262.40
Purchase #7	$48.63	10.821%	$53.8923	$53.89	$53.90	$53.90
7 purchase totals =	$1,085.85		$1,142.6242	$1,142.63	$1,142.60	$1,142.70