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	$211.43	13.633%	$240.2543	$240.25	$240.25	$240.30
Purchase #2	$52.58	9.310%	$57.4752	$57.48	$57.50	$57.50
Purchase #3	$204.97	13.751%	$233.1554	$233.16	$233.15	$233.20
Purchase #4	$150.45	9.111%	$164.1575	$164.16	$164.15	$164.20
Purchase #5	$187.78	12.806%	$211.8271	$211.83	$211.85	$211.80
Purchase #6	$66.42	4.321%	$69.29	$69.29	$69.30	$69.30
Purchase #7	$58.66	11.738%	$65.5455	$65.55	$65.55	$65.50
7 purchase totals =	$932.29		$1,041.7050	$1,041.72	$1,041.75	$1,041.80