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	$37.76	9.242%	$41.2498	$41.25	$41.25	$41.20
Purchase #2	$12.92	6.679%	$13.7829	$13.78	$13.80	$13.80
Purchase #3	$154.46	6.184%	$164.0118	$164.01	$164.00	$164.00
Purchase #4	$211.30	7.193%	$226.4988	$226.50	$226.50	$226.50
Purchase #5	$138.57	8.361%	$150.1558	$150.16	$150.15	$150.20
Purchase #6	$242.28	13.279%	$274.4524	$274.45	$274.45	$274.50
Purchase #7	$217.53	7.390%	$233.6055	$233.61	$233.60	$233.60
7 purchase totals =	$1,014.82		$1,103.7570	$1,103.76	$1,103.75	$1,103.80