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	$196.93	11.229%	$219.0433	$219.04	$219.05	$219.00
Purchase #2	$27.77	4.128%	$28.9163	$28.92	$28.90	$28.90
Purchase #3	$106.72	9.384%	$116.7346	$116.73	$116.75	$116.70
Purchase #4	$82.70	11.397%	$92.1253	$92.13	$92.15	$92.10
Purchase #5	$80.41	8.711%	$87.4145	$87.41	$87.40	$87.40
Purchase #6	$54.67	12.575%	$61.5448	$61.54	$61.55	$61.50
Purchase #7	$51.49	11.833%	$57.5828	$57.58	$57.60	$57.60
7 purchase totals =	$600.69		$663.3616	$663.35	$663.40	$663.20