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	$60.29	6.643%	$64.2951	$64.30	$64.30	$64.30
Purchase #2	$102.69	9.523%	$112.4692	$112.47	$112.45	$112.50
Purchase #3	$71.85	9.373%	$78.5845	$78.58	$78.60	$78.60
Purchase #4	$102.72	6.177%	$109.065	$109.07	$109.05	$109.10
Purchase #5	$55.44	13.325%	$62.8274	$62.83	$62.85	$62.80
Purchase #6	$74.53	11.853%	$83.364	$83.36	$83.35	$83.40
Purchase #7	$205.76	13.401%	$233.3339	$233.33	$233.35	$233.30
7 purchase totals =	$673.28		$743.9391	$743.94	$743.95	$744.00