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	$175.90	13.682%	$199.9666	$199.97	$199.95	$200.00
Purchase #2	$153.56	3.387%	$158.7611	$158.76	$158.75	$158.80
Purchase #3	$141.80	7.476%	$152.401	$152.40	$152.40	$152.40
Purchase #4	$174.34	5.769%	$184.3977	$184.40	$184.40	$184.40
Purchase #5	$90.42	11.223%	$100.5678	$100.57	$100.55	$100.60
Purchase #6	$99.66	5.131%	$104.7736	$104.77	$104.75	$104.80
Purchase #7	$235.95	5.777%	$249.5808	$249.58	$249.60	$249.60
7 purchase totals =	$1,071.63		$1,150.4486	$1,150.45	$1,150.40	$1,150.60