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	$114.56	7.782%	$123.4751	$123.48	$123.50	$123.50
Purchase #2	$145.51	13.367%	$164.9603	$164.96	$164.95	$165.00
Purchase #3	$219.59	5.643%	$231.9815	$231.98	$232.00	$232.00
Purchase #4	$62.65	5.350%	$66.0018	$66.00	$66.00	$66.00
Purchase #5	$68.58	5.123%	$72.0934	$72.09	$72.10	$72.10
Purchase #6	$40.81	10.472%	$45.0836	$45.08	$45.10	$45.10
Purchase #7	$161.72	9.371%	$176.8748	$176.87	$176.85	$176.90
7 purchase totals =	$813.42		$880.4705	$880.46	$880.50	$880.60