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	$216.44	13.719%	$246.1334	$246.13	$246.15	$246.10
Purchase #2	$73.74	7.587%	$79.3347	$79.33	$79.35	$79.30
Purchase #3	$147.25	13.806%	$167.5793	$167.58	$167.60	$167.60
Purchase #4	$107.86	8.319%	$116.8329	$116.83	$116.85	$116.80
Purchase #5	$227.91	9.658%	$249.9215	$249.92	$249.90	$249.90
Purchase #6	$146.61	9.471%	$160.4954	$160.50	$160.50	$160.50
Purchase #7	$165.50	6.617%	$176.4511	$176.45	$176.45	$176.50
7 purchase totals =	$1,085.31		$1,196.7483	$1,196.74	$1,196.80	$1,196.70