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	$152.25	11.253%	$169.3827	$169.38	$169.40	$169.40
Purchase #2	$130.64	4.466%	$136.4744	$136.47	$136.45	$136.50
Purchase #3	$42.51	8.451%	$46.1025	$46.10	$46.10	$46.10
Purchase #4	$153.65	3.539%	$159.0877	$159.09	$159.10	$159.10
Purchase #5	$66.94	11.450%	$74.6046	$74.60	$74.60	$74.60
Purchase #6	$98.45	4.142%	$102.5278	$102.53	$102.55	$102.50
Purchase #7	$128.34	10.866%	$142.2854	$142.29	$142.30	$142.30
7 purchase totals =	$772.78		$830.4651	$830.46	$830.50	$830.50