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	$118.92	8.167%	$128.6322	$128.63	$128.65	$128.60
Purchase #2	$50.90	4.274%	$53.0755	$53.08	$53.10	$53.10
Purchase #3	$37.42	6.833%	$39.9769	$39.98	$40.00	$40.00
Purchase #4	$169.31	5.208%	$178.1277	$178.13	$178.15	$178.10
Purchase #5	$52.34	8.302%	$56.6853	$56.69	$56.70	$56.70
Purchase #6	$50.27	5.709%	$53.1399	$53.14	$53.15	$53.10
Purchase #7	$188.81	5.549%	$199.2871	$199.29	$199.30	$199.30
7 purchase totals =	$667.97		$708.9246	$708.94	$709.05	$708.90