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	$218.81	5.864%	$231.641	$231.64	$231.65	$231.60
Purchase #2	$187.28	9.679%	$205.4068	$205.41	$205.40	$205.40
Purchase #3	$198.93	12.295%	$223.3884	$223.39	$223.40	$223.40
Purchase #4	$88.94	7.608%	$95.7066	$95.71	$95.70	$95.70
Purchase #5	$40.57	6.391%	$43.1628	$43.16	$43.15	$43.20
Purchase #6	$142.29	11.263%	$158.3161	$158.32	$158.30	$158.30
Purchase #7	$18.66	13.653%	$21.2076	$21.21	$21.20	$21.20
7 purchase totals =	$895.48		$978.8293	$978.84	$978.80	$978.80