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	$146.49	9.791%	$160.8328	$160.83	$160.85	$160.80
Purchase #2	$94.66	4.197%	$98.6329	$98.63	$98.65	$98.60
Purchase #3	$101.56	7.872%	$109.5548	$109.55	$109.55	$109.60
Purchase #4	$135.39	3.852%	$140.6052	$140.61	$140.60	$140.60
Purchase #5	$115.86	10.456%	$127.9743	$127.97	$127.95	$128.00
Purchase #6	$181.34	3.824%	$188.2744	$188.27	$188.25	$188.30
Purchase #7	$69.95	10.487%	$77.2857	$77.29	$77.30	$77.30
7 purchase totals =	$845.25		$903.1601	$903.15	$903.15	$903.20