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	$186.30	8.544%	$202.2175	$202.22	$202.20	$202.20
Purchase #2	$61.56	6.761%	$65.7221	$65.72	$65.70	$65.70
Purchase #3	$21.82	10.567%	$24.1257	$24.13	$24.15	$24.10
Purchase #4	$217.47	9.508%	$238.147	$238.15	$238.15	$238.10
Purchase #5	$148.28	13.758%	$168.6804	$168.68	$168.70	$168.70
Purchase #6	$39.72	4.524%	$41.5169	$41.52	$41.50	$41.50
Purchase #7	$113.63	4.361%	$118.5854	$118.59	$118.60	$118.60
7 purchase totals =	$788.78		$858.9950	$859.01	$859.00	$858.90