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	$40.94	7.246%	$43.9065	$43.91	$43.90	$43.90
Purchase #2	$57.28	4.355%	$59.7745	$59.77	$59.75	$59.80
Purchase #3	$126.82	3.827%	$131.6734	$131.67	$131.65	$131.70
Purchase #4	$86.86	12.380%	$97.6133	$97.61	$97.60	$97.60
Purchase #5	$79.34	3.434%	$82.0645	$82.06	$82.05	$82.10
Purchase #6	$118.70	12.647%	$133.712	$133.71	$133.70	$133.70
Purchase #7	$162.54	10.133%	$179.0102	$179.01	$179.00	$179.00
7 purchase totals =	$672.48		$727.7544	$727.74	$727.65	$727.80