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	$9.77	6.661%	$10.4208	$10.42	$10.40	$10.40
Purchase #2	$130.88	6.618%	$139.5416	$139.54	$139.55	$139.50
Purchase #3	$17.86	7.562%	$19.2106	$19.21	$19.20	$19.20
Purchase #4	$229.42	8.236%	$248.315	$248.32	$248.30	$248.30
Purchase #5	$111.32	7.846%	$120.0542	$120.05	$120.05	$120.10
Purchase #6	$83.56	3.680%	$86.635	$86.64	$86.65	$86.60
Purchase #7	$85.56	5.291%	$90.087	$90.09	$90.10	$90.10
7 purchase totals =	$668.37		$714.2642	$714.27	$714.25	$714.20