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	$106.50	5.503%	$112.3607	$112.36	$112.35	$112.40
Purchase #2	$239.56	13.657%	$272.2767	$272.28	$272.30	$272.30
Purchase #3	$144.25	11.487%	$160.82	$160.82	$160.80	$160.80
Purchase #4	$196.68	12.454%	$221.1745	$221.17	$221.15	$221.20
Purchase #5	$54.60	8.739%	$59.3715	$59.37	$59.35	$59.40
Purchase #6	$37.44	5.772%	$39.601	$39.60	$39.60	$39.60
Purchase #7	$214.40	7.331%	$230.1177	$230.12	$230.10	$230.10
7 purchase totals =	$993.43		$1,095.7221	$1,095.72	$1,095.65	$1,095.80