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	$109.61	4.565%	$114.6137	$114.61	$114.60	$114.60
Purchase #2	$16.52	5.151%	$17.3709	$17.37	$17.35	$17.40
Purchase #3	$135.54	12.208%	$152.0867	$152.09	$152.10	$152.10
Purchase #4	$241.54	3.870%	$250.8876	$250.89	$250.90	$250.90
Purchase #5	$42.51	5.637%	$44.9063	$44.91	$44.90	$44.90
Purchase #6	$99.38	13.295%	$112.5926	$112.59	$112.60	$112.60
Purchase #7	$243.84	5.330%	$256.8367	$256.84	$256.85	$256.80
7 purchase totals =	$888.94		$949.2945	$949.30	$949.30	$949.30