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	$245.58	5.817%	$259.8654	$259.87	$259.85	$259.90
Purchase #2	$30.63	13.610%	$34.7987	$34.80	$34.80	$34.80
Purchase #3	$225.69	5.366%	$237.8005	$237.80	$237.80	$237.80
Purchase #4	$180.97	8.786%	$196.87	$196.87	$196.85	$196.90
Purchase #5	$147.78	3.688%	$153.2301	$153.23	$153.25	$153.20
Purchase #6	$139.37	9.428%	$152.5098	$152.51	$152.50	$152.50
Purchase #7	$62.74	12.348%	$70.4871	$70.49	$70.50	$70.50
7 purchase totals =	$1,032.76		$1,105.5616	$1,105.57	$1,105.55	$1,105.60