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	$170.30	8.694%	$185.1059	$185.11	$185.10	$185.10
Purchase #2	$145.39	5.614%	$153.5522	$153.55	$153.55	$153.60
Purchase #3	$206.41	4.451%	$215.5973	$215.60	$215.60	$215.60
Purchase #4	$199.27	6.184%	$211.5929	$211.59	$211.60	$211.60
Purchase #5	$79.52	5.326%	$83.7552	$83.76	$83.75	$83.80
Purchase #6	$45.88	6.522%	$48.8723	$48.87	$48.85	$48.90
Purchase #7	$151.42	12.146%	$169.8115	$169.81	$169.80	$169.80
7 purchase totals =	$998.19		$1,068.2873	$1,068.29	$1,068.25	$1,068.40