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	$56.87	5.249%	$59.8551	$59.86	$59.85	$59.90
Purchase #2	$103.34	9.390%	$113.0436	$113.04	$113.05	$113.00
Purchase #3	$6.58	12.810%	$7.4229	$7.42	$7.40	$7.40
Purchase #4	$38.42	3.746%	$39.8592	$39.86	$39.85	$39.90
Purchase #5	$173.95	3.679%	$180.3496	$180.35	$180.35	$180.30
Purchase #6	$166.95	13.854%	$190.0793	$190.08	$190.10	$190.10
Purchase #7	$42.39	6.461%	$45.1288	$45.13	$45.15	$45.10
7 purchase totals =	$588.50		$635.7385	$635.74	$635.75	$635.70