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	$105.31	8.676%	$114.4467	$114.45	$114.45	$114.40
Purchase #2	$38.99	9.816%	$42.8173	$42.82	$42.80	$42.80
Purchase #3	$49.85	3.286%	$51.4881	$51.49	$51.50	$51.50
Purchase #4	$62.81	9.743%	$68.9296	$68.93	$68.95	$68.90
Purchase #5	$36.79	12.586%	$41.4204	$41.42	$41.40	$41.40
Purchase #6	$178.38	10.341%	$196.8263	$196.83	$196.85	$196.80
Purchase #7	$138.59	9.260%	$151.4234	$151.42	$151.40	$151.40
7 purchase totals =	$610.72		$667.3518	$667.36	$667.35	$667.20