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	$52.83	6.322%	$56.1699	$56.17	$56.15	$56.20
Purchase #2	$248.68	11.367%	$276.9475	$276.95	$276.95	$276.90
Purchase #3	$139.70	4.136%	$145.478	$145.48	$145.50	$145.50
Purchase #4	$60.31	11.682%	$67.3554	$67.36	$67.35	$67.40
Purchase #5	$198.65	12.451%	$223.3839	$223.38	$223.40	$223.40
Purchase #6	$112.78	10.833%	$124.9975	$125.00	$125.00	$125.00
Purchase #7	$100.88	7.477%	$108.4228	$108.42	$108.40	$108.40
7 purchase totals =	$913.83		$1,002.7550	$1,002.76	$1,002.75	$1,002.80