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	$96.46	11.208%	$107.2712	$107.27	$107.25	$107.30
Purchase #2	$247.94	5.610%	$261.8494	$261.85	$261.85	$261.80
Purchase #3	$149.59	12.707%	$168.5984	$168.60	$168.60	$168.60
Purchase #4	$170.68	8.746%	$185.6077	$185.61	$185.60	$185.60
Purchase #5	$46.38	8.356%	$50.2555	$50.26	$50.25	$50.30
Purchase #6	$58.79	11.217%	$65.3845	$65.38	$65.40	$65.40
Purchase #7	$248.93	9.449%	$272.4514	$272.45	$272.45	$272.50
7 purchase totals =	$1,018.77		$1,111.4181	$1,111.42	$1,111.40	$1,111.50