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	$215.50	5.462%	$227.2706	$227.27	$227.25	$227.30
Purchase #2	$120.51	6.492%	$128.3335	$128.33	$128.35	$128.30
Purchase #3	$73.80	13.127%	$83.4877	$83.49	$83.50	$83.50
Purchase #4	$155.40	11.107%	$172.6603	$172.66	$172.65	$172.70
Purchase #5	$37.97	10.740%	$42.048	$42.05	$42.05	$42.00
Purchase #6	$124.87	6.400%	$132.8617	$132.86	$132.85	$132.90
Purchase #7	$70.61	11.186%	$78.5084	$78.51	$78.50	$78.50
7 purchase totals =	$798.66		$865.1702	$865.17	$865.15	$865.20