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	$143.72	9.536%	$157.4251	$157.43	$157.45	$157.40
Purchase #2	$111.57	4.754%	$116.874	$116.87	$116.85	$116.90
Purchase #3	$150.25	6.147%	$159.4859	$159.49	$159.50	$159.50
Purchase #4	$83.92	9.428%	$91.832	$91.83	$91.85	$91.80
Purchase #5	$215.71	11.685%	$240.9157	$240.92	$240.90	$240.90
Purchase #6	$147.75	13.304%	$167.4067	$167.41	$167.40	$167.40
Purchase #7	$166.96	10.450%	$184.4073	$184.41	$184.40	$184.40
7 purchase totals =	$1,019.88		$1,118.3467	$1,118.36	$1,118.35	$1,118.30