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	$143.45	3.729%	$148.7993	$148.80	$148.80	$148.80
Purchase #2	$205.56	11.633%	$229.4728	$229.47	$229.45	$229.50
Purchase #3	$34.93	11.342%	$38.8918	$38.89	$38.90	$38.90
Purchase #4	$215.74	13.603%	$245.0871	$245.09	$245.10	$245.10
Purchase #5	$51.84	3.363%	$53.5834	$53.58	$53.60	$53.60
Purchase #6	$112.61	8.539%	$122.2258	$122.23	$122.25	$122.20
Purchase #7	$93.42	13.222%	$105.772	$105.77	$105.75	$105.80
7 purchase totals =	$857.55		$943.8322	$943.83	$943.85	$943.90