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	$226.51	8.520%	$245.8087	$245.81	$245.80	$245.80
Purchase #2	$148.72	5.147%	$156.3746	$156.37	$156.35	$156.40
Purchase #3	$31.82	5.677%	$33.6264	$33.63	$33.65	$33.60
Purchase #4	$99.71	4.338%	$104.0354	$104.04	$104.05	$104.00
Purchase #5	$14.76	7.249%	$15.83	$15.83	$15.85	$15.80
Purchase #6	$235.56	6.282%	$250.3579	$250.36	$250.35	$250.40
Purchase #7	$37.32	7.493%	$40.1164	$40.12	$40.10	$40.10
7 purchase totals =	$794.40		$846.1494	$846.16	$846.15	$846.10