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	$202.32	3.449%	$209.298	$209.30	$209.30	$209.30
Purchase #2	$95.43	10.247%	$105.2087	$105.21	$105.20	$105.20
Purchase #3	$217.92	10.510%	$240.8234	$240.82	$240.80	$240.80
Purchase #4	$107.25	9.825%	$117.7873	$117.79	$117.80	$117.80
Purchase #5	$101.38	10.784%	$112.3128	$112.31	$112.30	$112.30
Purchase #6	$199.54	13.171%	$225.8214	$225.82	$225.80	$225.80
Purchase #7	$132.51	9.454%	$145.0375	$145.04	$145.05	$145.00
7 purchase totals =	$1,056.35		$1,156.2891	$1,156.29	$1,156.25	$1,156.20