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	$99.75	9.595%	$109.321	$109.32	$109.30	$109.30
Purchase #2	$233.83	11.826%	$261.4827	$261.48	$261.50	$261.50
Purchase #3	$212.90	7.129%	$228.0776	$228.08	$228.10	$228.10
Purchase #4	$241.94	7.655%	$260.4605	$260.46	$260.45	$260.50
Purchase #5	$12.72	8.114%	$13.7521	$13.75	$13.75	$13.80
Purchase #6	$85.36	4.586%	$89.2746	$89.27	$89.25	$89.30
Purchase #7	$62.69	13.125%	$70.9181	$70.92	$70.90	$70.90
7 purchase totals =	$949.19		$1,033.2866	$1,033.28	$1,033.25	$1,033.40