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	$134.85	4.681%	$141.1623	$141.16	$141.15	$141.20
Purchase #2	$61.68	11.273%	$68.6332	$68.63	$68.65	$68.60
Purchase #3	$100.57	5.261%	$105.861	$105.86	$105.85	$105.90
Purchase #4	$220.52	11.241%	$245.3087	$245.31	$245.30	$245.30
Purchase #5	$66.77	8.258%	$72.2839	$72.28	$72.30	$72.30
Purchase #6	$22.93	8.132%	$24.7947	$24.79	$24.80	$24.80
Purchase #7	$141.56	3.152%	$146.022	$146.02	$146.00	$146.00
7 purchase totals =	$748.88		$804.0658	$804.05	$804.05	$804.10