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	$85.59	11.345%	$95.3002	$95.30	$95.30	$95.30
Purchase #2	$236.83	9.580%	$259.5183	$259.52	$259.50	$259.50
Purchase #3	$40.81	6.625%	$43.5137	$43.51	$43.50	$43.50
Purchase #4	$34.35	10.349%	$37.9049	$37.90	$37.90	$37.90
Purchase #5	$173.39	6.109%	$183.9824	$183.98	$184.00	$184.00
Purchase #6	$64.30	8.327%	$69.6543	$69.65	$69.65	$69.70
Purchase #7	$107.64	8.401%	$116.6828	$116.68	$116.70	$116.70
7 purchase totals =	$742.91		$806.5566	$806.54	$806.55	$806.60