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	$102.49	8.699%	$111.4056	$111.41	$111.40	$111.40
Purchase #2	$9.98	4.566%	$10.4357	$10.44	$10.45	$10.40
Purchase #3	$65.50	4.297%	$68.3145	$68.31	$68.30	$68.30
Purchase #4	$27.72	13.387%	$31.4309	$31.43	$31.45	$31.40
Purchase #5	$117.38	13.466%	$133.1864	$133.19	$133.20	$133.20
Purchase #6	$192.38	4.339%	$200.7274	$200.73	$200.75	$200.70
Purchase #7	$66.28	9.123%	$72.3267	$72.33	$72.35	$72.30
7 purchase totals =	$581.73		$627.8272	$627.84	$627.90	$627.70