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	$69.61	6.144%	$73.8868	$73.89	$73.90	$73.90
Purchase #2	$198.39	6.172%	$210.6346	$210.63	$210.65	$210.60
Purchase #3	$91.62	4.244%	$95.5084	$95.51	$95.50	$95.50
Purchase #4	$104.81	12.183%	$117.579	$117.58	$117.60	$117.60
Purchase #5	$179.41	6.531%	$191.1273	$191.13	$191.15	$191.10
Purchase #6	$44.68	13.224%	$50.5885	$50.59	$50.60	$50.60
Purchase #7	$42.75	5.866%	$45.2577	$45.26	$45.25	$45.30
7 purchase totals =	$731.27		$784.5823	$784.59	$784.65	$784.60