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	$31.46	7.439%	$33.8003	$33.80	$33.80	$33.80
Purchase #2	$6.31	4.378%	$6.5863	$6.59	$6.60	$6.60
Purchase #3	$126.93	4.414%	$132.5327	$132.53	$132.55	$132.50
Purchase #4	$178.37	7.301%	$191.3928	$191.39	$191.40	$191.40
Purchase #5	$95.47	10.670%	$105.6566	$105.66	$105.65	$105.70
Purchase #6	$141.88	4.653%	$148.4817	$148.48	$148.50	$148.50
Purchase #7	$163.26	9.726%	$179.1387	$179.14	$179.15	$179.10
7 purchase totals =	$743.68		$797.5891	$797.59	$797.65	$797.60