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	$29.39	11.710%	$32.8316	$32.83	$32.85	$32.80
Purchase #2	$51.94	4.125%	$54.0825	$54.08	$54.10	$54.10
Purchase #3	$15.52	7.140%	$16.6281	$16.63	$16.65	$16.60
Purchase #4	$148.49	13.238%	$168.1471	$168.15	$168.15	$168.10
Purchase #5	$247.28	4.560%	$258.556	$258.56	$258.55	$258.60
Purchase #6	$221.37	3.381%	$228.8545	$228.85	$228.85	$228.90
Purchase #7	$226.54	11.191%	$251.8921	$251.89	$251.90	$251.90
7 purchase totals =	$940.53		$1,010.9919	$1,010.99	$1,011.05	$1,011.00