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	$136.71	9.767%	$150.0625	$150.06	$150.05	$150.10
Purchase #2	$12.45	6.719%	$13.2865	$13.29	$13.30	$13.30
Purchase #3	$85.42	8.707%	$92.8575	$92.86	$92.85	$92.90
Purchase #4	$192.56	12.419%	$216.474	$216.47	$216.45	$216.50
Purchase #5	$175.92	11.739%	$196.5712	$196.57	$196.55	$196.60
Purchase #6	$81.28	10.828%	$90.081	$90.08	$90.10	$90.10
Purchase #7	$80.72	4.454%	$84.3153	$84.32	$84.30	$84.30
7 purchase totals =	$765.06		$843.6480	$843.65	$843.60	$843.80