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	$141.78	5.589%	$149.7041	$149.70	$149.70	$149.70
Purchase #2	$72.58	11.102%	$80.6378	$80.64	$80.65	$80.60
Purchase #3	$156.38	6.825%	$167.0529	$167.05	$167.05	$167.10
Purchase #4	$57.25	4.202%	$59.6556	$59.66	$59.65	$59.70
Purchase #5	$130.80	11.539%	$145.893	$145.89	$145.90	$145.90
Purchase #6	$133.78	7.583%	$143.9245	$143.92	$143.90	$143.90
Purchase #7	$149.60	5.696%	$158.1212	$158.12	$158.10	$158.10
7 purchase totals =	$842.17		$904.9891	$904.98	$904.95	$905.00