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	$24.96	4.317%	$26.0375	$26.04	$26.05	$26.00
Purchase #2	$99.56	5.106%	$104.6435	$104.64	$104.65	$104.60
Purchase #3	$71.27	10.752%	$78.933	$78.93	$78.95	$78.90
Purchase #4	$171.56	6.834%	$183.2844	$183.28	$183.30	$183.30
Purchase #5	$78.89	5.158%	$82.9591	$82.96	$82.95	$83.00
Purchase #6	$16.35	4.304%	$17.0537	$17.05	$17.05	$17.10
Purchase #7	$64.29	3.587%	$66.5961	$66.60	$66.60	$66.60
7 purchase totals =	$526.88		$559.5073	$559.50	$559.55	$559.50