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	$146.40	6.476%	$155.8809	$155.88	$155.90	$155.90
Purchase #2	$150.57	3.638%	$156.0477	$156.05	$156.05	$156.00
Purchase #3	$158.92	13.552%	$180.4568	$180.46	$180.45	$180.50
Purchase #4	$90.33	7.665%	$97.2538	$97.25	$97.25	$97.30
Purchase #5	$176.56	12.577%	$198.766	$198.77	$198.75	$198.80
Purchase #6	$50.74	3.260%	$52.3941	$52.39	$52.40	$52.40
Purchase #7	$64.35	3.698%	$66.7297	$66.73	$66.75	$66.70
7 purchase totals =	$837.87		$907.5290	$907.53	$907.55	$907.60