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	$113.42	11.104%	$126.0142	$126.01	$126.00	$126.00
Purchase #2	$234.35	5.744%	$247.8111	$247.81	$247.80	$247.80
Purchase #3	$57.58	3.219%	$59.4335	$59.43	$59.45	$59.40
Purchase #4	$92.65	10.342%	$102.2319	$102.23	$102.25	$102.20
Purchase #5	$61.85	13.494%	$70.196	$70.20	$70.20	$70.20
Purchase #6	$52.52	4.474%	$54.8697	$54.87	$54.85	$54.90
Purchase #7	$95.91	10.403%	$105.8875	$105.89	$105.90	$105.90
7 purchase totals =	$708.28		$766.4439	$766.44	$766.45	$766.40