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	$151.56	3.367%	$156.663	$156.66	$156.65	$156.70
Purchase #2	$86.74	11.698%	$96.8868	$96.89	$96.90	$96.90
Purchase #3	$59.61	11.799%	$66.6434	$66.64	$66.65	$66.60
Purchase #4	$48.79	4.152%	$50.8158	$50.82	$50.80	$50.80
Purchase #5	$182.71	13.113%	$206.6688	$206.67	$206.65	$206.70
Purchase #6	$55.37	8.288%	$59.9591	$59.96	$59.95	$60.00
Purchase #7	$56.62	11.514%	$63.1392	$63.14	$63.15	$63.10
7 purchase totals =	$641.40		$700.7761	$700.78	$700.75	$700.80