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	$50.69	4.107%	$52.7718	$52.77	$52.75	$52.80
Purchase #2	$184.93	5.345%	$194.8145	$194.81	$194.80	$194.80
Purchase #3	$81.76	8.134%	$88.4104	$88.41	$88.40	$88.40
Purchase #4	$128.52	12.690%	$144.8292	$144.83	$144.85	$144.80
Purchase #5	$138.93	4.581%	$145.2944	$145.29	$145.30	$145.30
Purchase #6	$208.40	9.114%	$227.3936	$227.39	$227.40	$227.40
Purchase #7	$224.82	3.726%	$233.1968	$233.20	$233.20	$233.20
7 purchase totals =	$1,018.05		$1,086.7107	$1,086.70	$1,086.70	$1,086.70