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	$168.72	10.113%	$185.7827	$185.78	$185.80	$185.80
Purchase #2	$145.63	9.353%	$159.2508	$159.25	$159.25	$159.30
Purchase #3	$155.25	10.758%	$171.9518	$171.95	$171.95	$172.00
Purchase #4	$250.29	10.475%	$276.5079	$276.51	$276.50	$276.50
Purchase #5	$95.90	13.470%	$108.8177	$108.82	$108.80	$108.80
Purchase #6	$129.96	11.709%	$145.177	$145.18	$145.20	$145.20
Purchase #7	$105.33	5.223%	$110.8314	$110.83	$110.85	$110.80
7 purchase totals =	$1,051.08		$1,158.3193	$1,158.32	$1,158.35	$1,158.40