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	$205.43	6.103%	$217.9674	$217.97	$217.95	$218.00
Purchase #2	$164.30	11.127%	$182.5817	$182.58	$182.60	$182.60
Purchase #3	$241.91	4.825%	$253.5822	$253.58	$253.60	$253.60
Purchase #4	$117.77	11.727%	$131.5809	$131.58	$131.60	$131.60
Purchase #5	$122.89	6.756%	$131.1924	$131.19	$131.20	$131.20
Purchase #6	$158.85	5.112%	$166.9704	$166.97	$166.95	$167.00
Purchase #7	$60.61	6.430%	$64.5072	$64.51	$64.50	$64.50
7 purchase totals =	$1,071.76		$1,148.3822	$1,148.38	$1,148.40	$1,148.50