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	$211.42	12.496%	$237.839	$237.84	$237.85	$237.80
Purchase #2	$207.25	13.534%	$235.2992	$235.30	$235.30	$235.30
Purchase #3	$37.72	12.844%	$42.5648	$42.56	$42.55	$42.60
Purchase #4	$105.65	13.653%	$120.0744	$120.07	$120.05	$120.10
Purchase #5	$188.36	6.582%	$200.7579	$200.76	$200.75	$200.80
Purchase #6	$54.47	10.556%	$60.2199	$60.22	$60.20	$60.20
Purchase #7	$151.52	8.624%	$164.5871	$164.59	$164.60	$164.60
7 purchase totals =	$956.39		$1,061.3423	$1,061.34	$1,061.30	$1,061.40