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	$125.94	3.592%	$130.4638	$130.46	$130.45	$130.50
Purchase #2	$50.73	9.429%	$55.5133	$55.51	$55.50	$55.50
Purchase #3	$42.63	5.202%	$44.8476	$44.85	$44.85	$44.80
Purchase #4	$176.59	11.298%	$196.5411	$196.54	$196.55	$196.50
Purchase #5	$227.92	11.367%	$253.8277	$253.83	$253.85	$253.80
Purchase #6	$108.58	9.113%	$118.4749	$118.47	$118.45	$118.50
Purchase #7	$100.44	7.788%	$108.2623	$108.26	$108.25	$108.30
7 purchase totals =	$832.83		$907.9307	$907.92	$907.90	$907.90