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	$72.31	5.664%	$76.4056	$76.41	$76.40	$76.40
Purchase #2	$45.92	10.602%	$50.7884	$50.79	$50.80	$50.80
Purchase #3	$226.89	13.728%	$258.0375	$258.04	$258.05	$258.00
Purchase #4	$59.66	12.778%	$67.2834	$67.28	$67.30	$67.30
Purchase #5	$19.82	10.161%	$21.8339	$21.83	$21.85	$21.80
Purchase #6	$233.28	7.847%	$251.5855	$251.59	$251.60	$251.60
Purchase #7	$6.74	11.161%	$7.4923	$7.49	$7.50	$7.50
7 purchase totals =	$664.62		$733.4266	$733.43	$733.50	$733.40