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	$228.85	7.121%	$245.1464	$245.15	$245.15	$245.10
Purchase #2	$201.50	11.733%	$225.142	$225.14	$225.15	$225.10
Purchase #3	$101.90	6.604%	$108.6295	$108.63	$108.65	$108.60
Purchase #4	$171.56	11.554%	$191.382	$191.38	$191.40	$191.40
Purchase #5	$205.37	11.517%	$229.0225	$229.02	$229.00	$229.00
Purchase #6	$186.81	12.286%	$209.7615	$209.76	$209.75	$209.80
Purchase #7	$54.92	9.147%	$59.9435	$59.94	$59.95	$59.90
7 purchase totals =	$1,150.91		$1,269.0274	$1,269.02	$1,269.05	$1,268.90