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	$98.56	11.104%	$109.5041	$109.50	$109.50	$109.50
Purchase #2	$12.63	6.594%	$13.4628	$13.46	$13.45	$13.50
Purchase #3	$96.82	4.189%	$100.8758	$100.88	$100.90	$100.90
Purchase #4	$97.66	3.863%	$101.4326	$101.43	$101.45	$101.40
Purchase #5	$18.62	11.104%	$20.6876	$20.69	$20.70	$20.70
Purchase #6	$138.29	3.244%	$142.7761	$142.78	$142.80	$142.80
Purchase #7	$85.45	9.863%	$93.8779	$93.88	$93.90	$93.90
7 purchase totals =	$548.03		$582.6169	$582.62	$582.70	$582.70