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	$41.86	3.665%	$43.3942	$43.39	$43.40	$43.40
Purchase #2	$128.35	8.600%	$139.3881	$139.39	$139.40	$139.40
Purchase #3	$10.39	8.185%	$11.2404	$11.24	$11.25	$11.20
Purchase #4	$156.31	7.784%	$168.4772	$168.48	$168.50	$168.50
Purchase #5	$59.32	3.500%	$61.3962	$61.40	$61.40	$61.40
Purchase #6	$240.68	6.764%	$256.9596	$256.96	$256.95	$257.00
Purchase #7	$75.26	5.736%	$79.5769	$79.58	$79.60	$79.60
7 purchase totals =	$712.17		$760.4326	$760.44	$760.50	$760.50