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	$35.92	4.632%	$37.5838	$37.58	$37.60	$37.60
Purchase #2	$151.86	5.188%	$159.7385	$159.74	$159.75	$159.70
Purchase #3	$10.44	9.585%	$11.4407	$11.44	$11.45	$11.40
Purchase #4	$15.74	5.262%	$16.5682	$16.57	$16.55	$16.60
Purchase #5	$185.98	10.383%	$205.2903	$205.29	$205.30	$205.30
Purchase #6	$109.47	13.166%	$123.8828	$123.88	$123.90	$123.90
Purchase #7	$226.89	7.339%	$243.5415	$243.54	$243.55	$243.50
7 purchase totals =	$736.30		$798.0458	$798.04	$798.10	$798.00