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	$46.72	13.872%	$53.201	$53.20	$53.20	$53.20
Purchase #2	$62.80	3.323%	$64.8868	$64.89	$64.90	$64.90
Purchase #3	$95.51	10.256%	$105.3055	$105.31	$105.30	$105.30
Purchase #4	$173.49	12.316%	$194.857	$194.86	$194.85	$194.90
Purchase #5	$235.91	13.291%	$267.2648	$267.26	$267.25	$267.30
Purchase #6	$234.32	3.733%	$243.0672	$243.07	$243.05	$243.10
Purchase #7	$168.39	7.600%	$181.1876	$181.19	$181.20	$181.20
7 purchase totals =	$1,017.14		$1,109.7699	$1,109.78	$1,109.75	$1,109.90