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	$50.69	9.370%	$55.4397	$55.44	$55.45	$55.40
Purchase #2	$141.54	5.284%	$149.019	$149.02	$149.00	$149.00
Purchase #3	$54.51	8.776%	$59.2938	$59.29	$59.30	$59.30
Purchase #4	$82.58	3.508%	$85.4769	$85.48	$85.50	$85.50
Purchase #5	$174.69	10.191%	$192.4927	$192.49	$192.50	$192.50
Purchase #6	$172.91	13.639%	$196.4932	$196.49	$196.50	$196.50
Purchase #7	$154.46	10.311%	$170.3864	$170.39	$170.40	$170.40
7 purchase totals =	$831.38		$908.6017	$908.60	$908.65	$908.60