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	$167.38	13.457%	$189.9043	$189.90	$189.90	$189.90
Purchase #2	$132.95	8.409%	$144.1298	$144.13	$144.15	$144.10
Purchase #3	$17.98	5.447%	$18.9594	$18.96	$18.95	$19.00
Purchase #4	$54.29	12.374%	$61.0078	$61.01	$61.00	$61.00
Purchase #5	$177.79	10.446%	$196.3619	$196.36	$196.35	$196.40
Purchase #6	$172.49	5.234%	$181.5181	$181.52	$181.50	$181.50
Purchase #7	$120.99	13.463%	$137.2789	$137.28	$137.30	$137.30
7 purchase totals =	$843.87		$929.1602	$929.16	$929.15	$929.20