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	$140.63	6.446%	$149.695	$149.70	$149.70	$149.70
Purchase #2	$89.43	6.572%	$95.3073	$95.31	$95.30	$95.30
Purchase #3	$103.93	7.635%	$111.8651	$111.87	$111.85	$111.90
Purchase #4	$85.42	6.180%	$90.699	$90.70	$90.70	$90.70
Purchase #5	$116.90	6.354%	$124.3278	$124.33	$124.35	$124.30
Purchase #6	$9.83	4.376%	$10.2602	$10.26	$10.25	$10.30
Purchase #7	$42.43	4.865%	$44.4942	$44.49	$44.50	$44.50
7 purchase totals =	$588.57		$626.6486	$626.66	$626.65	$626.70