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	$133.65	10.444%	$147.6084	$147.61	$147.60	$147.60
Purchase #2	$78.33	13.373%	$88.8051	$88.81	$88.80	$88.80
Purchase #3	$72.77	9.659%	$79.7989	$79.80	$79.80	$79.80
Purchase #4	$46.87	4.245%	$48.8596	$48.86	$48.85	$48.90
Purchase #5	$123.48	4.162%	$128.6192	$128.62	$128.60	$128.60
Purchase #6	$55.66	6.486%	$59.2701	$59.27	$59.25	$59.30
Purchase #7	$62.60	10.530%	$69.1918	$69.19	$69.20	$69.20
7 purchase totals =	$573.36		$622.1531	$622.16	$622.10	$622.20