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	$176.27	11.212%	$196.0334	$196.03	$196.05	$196.00
Purchase #2	$32.96	12.259%	$37.0006	$37.00	$37.00	$37.00
Purchase #3	$145.42	10.778%	$161.0934	$161.09	$161.10	$161.10
Purchase #4	$12.77	3.141%	$13.1711	$13.17	$13.15	$13.20
Purchase #5	$91.32	13.704%	$103.8345	$103.83	$103.85	$103.80
Purchase #6	$209.29	10.469%	$231.2006	$231.20	$231.20	$231.20
Purchase #7	$128.51	7.512%	$138.1637	$138.16	$138.15	$138.20
7 purchase totals =	$796.54		$880.4973	$880.48	$880.50	$880.50