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	$6.98	8.338%	$7.562	$7.56	$7.55	$7.60
Purchase #2	$190.78	12.303%	$214.2517	$214.25	$214.25	$214.30
Purchase #3	$38.30	11.466%	$42.6915	$42.69	$42.70	$42.70
Purchase #4	$248.85	13.497%	$282.4373	$282.44	$282.45	$282.40
Purchase #5	$201.86	7.652%	$217.3063	$217.31	$217.30	$217.30
Purchase #6	$96.49	4.139%	$100.4837	$100.48	$100.50	$100.50
Purchase #7	$206.74	10.205%	$227.8378	$227.84	$227.85	$227.80
7 purchase totals =	$990.00		$1,092.5703	$1,092.57	$1,092.60	$1,092.60