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	$145.88	10.618%	$161.3695	$161.37	$161.35	$161.40
Purchase #2	$33.64	5.126%	$35.3644	$35.36	$35.35	$35.40
Purchase #3	$248.32	5.632%	$262.3054	$262.31	$262.30	$262.30
Purchase #4	$66.42	9.820%	$72.9424	$72.94	$72.95	$72.90
Purchase #5	$212.87	9.714%	$233.5482	$233.55	$233.55	$233.50
Purchase #6	$75.52	9.781%	$82.9066	$82.91	$82.90	$82.90
Purchase #7	$41.63	9.640%	$45.6431	$45.64	$45.65	$45.60
7 purchase totals =	$824.28		$894.0796	$894.08	$894.05	$894.00