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	$131.68	12.648%	$148.3349	$148.33	$148.35	$148.30
Purchase #2	$158.41	11.637%	$176.8442	$176.84	$176.85	$176.80
Purchase #3	$162.27	3.856%	$168.5271	$168.53	$168.55	$168.50
Purchase #4	$153.70	8.245%	$166.3726	$166.37	$166.35	$166.40
Purchase #5	$216.50	5.140%	$227.6281	$227.63	$227.65	$227.60
Purchase #6	$165.31	4.662%	$173.0168	$173.02	$173.00	$173.00
Purchase #7	$37.58	13.257%	$42.562	$42.56	$42.55	$42.60
7 purchase totals =	$1,025.45		$1,103.2857	$1,103.28	$1,103.30	$1,103.20