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	$141.53	4.463%	$147.8465	$147.85	$147.85	$147.80
Purchase #2	$182.35	6.527%	$194.252	$194.25	$194.25	$194.30
Purchase #3	$55.77	6.711%	$59.5127	$59.51	$59.50	$59.50
Purchase #4	$244.53	11.390%	$272.382	$272.38	$272.40	$272.40
Purchase #5	$129.60	12.371%	$145.6328	$145.63	$145.65	$145.60
Purchase #6	$135.65	8.326%	$146.9442	$146.94	$146.95	$146.90
Purchase #7	$152.59	8.473%	$165.519	$165.52	$165.50	$165.50
7 purchase totals =	$1,042.02		$1,132.0892	$1,132.08	$1,132.10	$1,132.00