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	$186.72	7.252%	$200.2609	$200.26	$200.25	$200.30
Purchase #2	$132.48	8.124%	$143.2427	$143.24	$143.25	$143.20
Purchase #3	$111.56	3.487%	$115.4501	$115.45	$115.45	$115.50
Purchase #4	$233.48	12.611%	$262.9242	$262.92	$262.90	$262.90
Purchase #5	$18.42	11.820%	$20.5972	$20.60	$20.60	$20.60
Purchase #6	$93.74	5.762%	$99.1413	$99.14	$99.15	$99.10
Purchase #7	$227.98	4.149%	$237.4389	$237.44	$237.45	$237.40
7 purchase totals =	$1,004.38		$1,079.0553	$1,079.05	$1,079.05	$1,079.00