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	$96.53	5.563%	$101.9	$101.90	$101.90	$101.90
Purchase #2	$170.39	3.585%	$176.4985	$176.50	$176.50	$176.50
Purchase #3	$43.50	4.418%	$45.4218	$45.42	$45.40	$45.40
Purchase #4	$63.68	4.285%	$66.4087	$66.41	$66.40	$66.40
Purchase #5	$175.58	7.610%	$188.9416	$188.94	$188.95	$188.90
Purchase #6	$191.85	10.446%	$211.8907	$211.89	$211.90	$211.90
Purchase #7	$152.45	10.484%	$168.4329	$168.43	$168.45	$168.40
7 purchase totals =	$893.98		$959.4942	$959.49	$959.50	$959.40