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	$197.39	5.591%	$208.4261	$208.43	$208.45	$208.40
Purchase #2	$183.74	12.403%	$206.5293	$206.53	$206.55	$206.50
Purchase #3	$222.69	3.140%	$229.6825	$229.68	$229.70	$229.70
Purchase #4	$72.66	5.250%	$76.4747	$76.47	$76.45	$76.50
Purchase #5	$139.30	13.413%	$157.9843	$157.98	$158.00	$158.00
Purchase #6	$47.85	4.130%	$49.8262	$49.83	$49.85	$49.80
Purchase #7	$83.98	6.337%	$89.3018	$89.30	$89.30	$89.30
7 purchase totals =	$947.61		$1,018.2249	$1,018.22	$1,018.30	$1,018.20