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	$22.74	3.673%	$23.5752	$23.58	$23.60	$23.60
Purchase #2	$108.51	3.425%	$112.2265	$112.23	$112.25	$112.20
Purchase #3	$214.73	10.850%	$238.0282	$238.03	$238.05	$238.00
Purchase #4	$52.76	12.871%	$59.5507	$59.55	$59.55	$59.60
Purchase #5	$59.93	4.144%	$62.4135	$62.41	$62.40	$62.40
Purchase #6	$88.38	4.204%	$92.0955	$92.10	$92.10	$92.10
Purchase #7	$78.53	11.562%	$87.6096	$87.61	$87.60	$87.60
7 purchase totals =	$625.58		$675.4992	$675.51	$675.55	$675.50