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	$139.62	4.463%	$145.8512	$145.85	$145.85	$145.90
Purchase #2	$138.81	4.368%	$144.8732	$144.87	$144.85	$144.90
Purchase #3	$10.85	8.721%	$11.7962	$11.80	$11.80	$11.80
Purchase #4	$238.82	9.543%	$261.6106	$261.61	$261.60	$261.60
Purchase #5	$53.47	11.871%	$59.8174	$59.82	$59.80	$59.80
Purchase #6	$36.74	13.742%	$41.7888	$41.79	$41.80	$41.80
Purchase #7	$90.74	3.375%	$93.8025	$93.80	$93.80	$93.80
7 purchase totals =	$709.05		$759.5399	$759.54	$759.50	$759.60