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	$37.68	13.557%	$42.7883	$42.79	$42.80	$42.80
Purchase #2	$87.36	8.836%	$95.0791	$95.08	$95.10	$95.10
Purchase #3	$105.86	12.353%	$118.9369	$118.94	$118.95	$118.90
Purchase #4	$158.54	4.174%	$165.1575	$165.16	$165.15	$165.20
Purchase #5	$111.26	11.197%	$123.7178	$123.72	$123.70	$123.70
Purchase #6	$141.78	8.850%	$154.3275	$154.33	$154.35	$154.30
Purchase #7	$69.28	11.234%	$77.0629	$77.06	$77.05	$77.10
7 purchase totals =	$711.76		$777.0700	$777.08	$777.10	$777.10