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	$208.42	11.690%	$232.7843	$232.78	$232.80	$232.80
Purchase #2	$19.45	6.362%	$20.6874	$20.69	$20.70	$20.70
Purchase #3	$37.62	10.618%	$41.6145	$41.61	$41.60	$41.60
Purchase #4	$18.44	10.596%	$20.3939	$20.39	$20.40	$20.40
Purchase #5	$92.68	8.532%	$100.5875	$100.59	$100.60	$100.60
Purchase #6	$172.99	8.544%	$187.7703	$187.77	$187.75	$187.80
Purchase #7	$23.89	13.149%	$27.0313	$27.03	$27.05	$27.00
7 purchase totals =	$573.49		$630.8692	$630.86	$630.90	$630.90