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	$55.48	7.438%	$59.6066	$59.61	$59.60	$59.60
Purchase #2	$210.41	3.181%	$217.1031	$217.10	$217.10	$217.10
Purchase #3	$31.64	10.550%	$34.978	$34.98	$35.00	$35.00
Purchase #4	$63.28	5.599%	$66.823	$66.82	$66.80	$66.80
Purchase #5	$179.83	10.765%	$199.1887	$199.19	$199.20	$199.20
Purchase #6	$185.59	10.742%	$205.5261	$205.53	$205.55	$205.50
Purchase #7	$133.26	12.693%	$150.1747	$150.17	$150.15	$150.20
7 purchase totals =	$859.49		$933.4002	$933.40	$933.40	$933.40