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	$176.26	8.126%	$190.5829	$190.58	$190.60	$190.60
Purchase #2	$127.33	3.215%	$131.4237	$131.42	$131.40	$131.40
Purchase #3	$247.74	8.383%	$268.508	$268.51	$268.50	$268.50
Purchase #4	$250.96	5.142%	$263.8644	$263.86	$263.85	$263.90
Purchase #5	$40.39	4.733%	$42.3017	$42.30	$42.30	$42.30
Purchase #6	$48.94	10.263%	$53.9627	$53.96	$53.95	$54.00
Purchase #7	$178.44	5.304%	$187.9045	$187.90	$187.90	$187.90
7 purchase totals =	$1,070.06		$1,138.5479	$1,138.53	$1,138.50	$1,138.60