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	$157.37	10.606%	$174.0607	$174.06	$174.05	$174.10
Purchase #2	$25.37	7.388%	$27.2443	$27.24	$27.25	$27.20
Purchase #3	$184.69	3.359%	$190.8937	$190.89	$190.90	$190.90
Purchase #4	$100.54	6.380%	$106.9545	$106.95	$106.95	$107.00
Purchase #5	$87.92	3.411%	$90.919	$90.92	$90.90	$90.90
Purchase #6	$114.81	8.688%	$124.7847	$124.78	$124.80	$124.80
Purchase #7	$83.42	8.275%	$90.323	$90.32	$90.30	$90.30
7 purchase totals =	$754.12		$805.1799	$805.16	$805.15	$805.20