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	$24.46	6.817%	$26.1274	$26.13	$26.15	$26.10
Purchase #2	$116.87	9.427%	$127.8873	$127.89	$127.90	$127.90
Purchase #3	$124.85	3.105%	$128.7266	$128.73	$128.75	$128.70
Purchase #4	$103.25	13.377%	$117.0618	$117.06	$117.05	$117.10
Purchase #5	$27.32	7.832%	$29.4597	$29.46	$29.45	$29.50
Purchase #6	$237.86	5.159%	$250.1312	$250.13	$250.15	$250.10
Purchase #7	$74.68	8.555%	$81.0689	$81.07	$81.05	$81.10
7 purchase totals =	$709.29		$760.4629	$760.47	$760.50	$760.50