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	$176.34	5.476%	$185.9964	$186.00	$186.00	$186.00
Purchase #2	$147.94	4.176%	$154.118	$154.12	$154.10	$154.10
Purchase #3	$29.87	9.758%	$32.7847	$32.78	$32.80	$32.80
Purchase #4	$214.44	4.263%	$223.5816	$223.58	$223.60	$223.60
Purchase #5	$135.71	12.380%	$152.5109	$152.51	$152.50	$152.50
Purchase #6	$145.72	3.453%	$150.7517	$150.75	$150.75	$150.80
Purchase #7	$50.98	7.767%	$54.9396	$54.94	$54.95	$54.90
7 purchase totals =	$901.00		$954.6829	$954.68	$954.70	$954.70