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	$172.61	11.592%	$192.619	$192.62	$192.60	$192.60
Purchase #2	$88.66	5.403%	$93.4503	$93.45	$93.45	$93.50
Purchase #3	$91.77	9.624%	$100.6019	$100.60	$100.60	$100.60
Purchase #4	$23.78	8.399%	$25.7773	$25.78	$25.80	$25.80
Purchase #5	$164.94	7.673%	$177.5958	$177.60	$177.60	$177.60
Purchase #6	$118.26	8.739%	$128.5947	$128.59	$128.60	$128.60
Purchase #7	$95.78	6.404%	$101.9138	$101.91	$101.90	$101.90
7 purchase totals =	$755.80		$820.5528	$820.55	$820.55	$820.60