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	$95.64	10.184%	$105.38	$105.38	$105.40	$105.40
Purchase #2	$224.85	10.517%	$248.4975	$248.50	$248.50	$248.50
Purchase #3	$44.48	13.204%	$50.3531	$50.35	$50.35	$50.40
Purchase #4	$165.25	11.774%	$184.7065	$184.71	$184.70	$184.70
Purchase #5	$112.99	12.729%	$127.3725	$127.37	$127.35	$127.40
Purchase #6	$155.57	7.429%	$167.1273	$167.13	$167.15	$167.10
Purchase #7	$101.38	9.500%	$111.0111	$111.01	$111.00	$111.00
7 purchase totals =	$900.16		$994.4480	$994.45	$994.45	$994.50