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	$105.33	5.431%	$111.0505	$111.05	$111.05	$111.10
Purchase #2	$109.63	9.658%	$120.2181	$120.22	$120.20	$120.20
Purchase #3	$224.25	5.782%	$237.2161	$237.22	$237.20	$237.20
Purchase #4	$75.79	9.203%	$82.765	$82.77	$82.75	$82.80
Purchase #5	$81.67	8.358%	$88.496	$88.50	$88.50	$88.50
Purchase #6	$237.64	10.504%	$262.6017	$262.60	$262.60	$262.60
Purchase #7	$73.74	6.389%	$78.4512	$78.45	$78.45	$78.50
7 purchase totals =	$908.05		$980.7986	$980.81	$980.75	$980.90