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	$59.83	9.555%	$65.5468	$65.55	$65.55	$65.50
Purchase #2	$17.71	6.118%	$18.7935	$18.79	$18.80	$18.80
Purchase #3	$22.98	4.746%	$24.0706	$24.07	$24.05	$24.10
Purchase #4	$156.33	10.229%	$172.321	$172.32	$172.30	$172.30
Purchase #5	$19.55	7.434%	$21.0033	$21.00	$21.00	$21.00
Purchase #6	$84.53	7.294%	$90.6956	$90.70	$90.70	$90.70
Purchase #7	$14.29	13.786%	$16.26	$16.26	$16.25	$16.30
7 purchase totals =	$375.22		$408.6908	$408.69	$408.65	$408.70