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	$191.74	13.609%	$217.8339	$217.83	$217.85	$217.80
Purchase #2	$188.66	10.821%	$209.0749	$209.07	$209.05	$209.10
Purchase #3	$235.34	4.434%	$245.775	$245.78	$245.80	$245.80
Purchase #4	$105.83	10.491%	$116.9326	$116.93	$116.95	$116.90
Purchase #5	$92.32	4.629%	$96.5935	$96.59	$96.60	$96.60
Purchase #6	$74.28	6.247%	$78.9203	$78.92	$78.90	$78.90
Purchase #7	$124.33	11.348%	$138.439	$138.44	$138.45	$138.40
7 purchase totals =	$1,012.50		$1,103.5692	$1,103.56	$1,103.60	$1,103.50