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	$93.66	4.828%	$98.1819	$98.18	$98.20	$98.20
Purchase #2	$190.32	5.401%	$200.5992	$200.60	$200.60	$200.60
Purchase #3	$51.78	4.499%	$54.1096	$54.11	$54.10	$54.10
Purchase #4	$126.61	3.523%	$131.0705	$131.07	$131.05	$131.10
Purchase #5	$53.50	3.371%	$55.3035	$55.30	$55.30	$55.30
Purchase #6	$5.29	5.246%	$5.5675	$5.57	$5.55	$5.60
Purchase #7	$19.87	8.255%	$21.5103	$21.51	$21.50	$21.50
7 purchase totals =	$541.03		$566.3425	$566.34	$566.30	$566.40