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	$86.61	11.266%	$96.3675	$96.37	$96.35	$96.40
Purchase #2	$150.91	11.322%	$167.996	$168.00	$168.00	$168.00
Purchase #3	$95.86	7.632%	$103.176	$103.18	$103.20	$103.20
Purchase #4	$14.98	3.467%	$15.4994	$15.50	$15.50	$15.50
Purchase #5	$196.29	10.691%	$217.2754	$217.28	$217.30	$217.30
Purchase #6	$163.81	9.476%	$179.3326	$179.33	$179.35	$179.30
Purchase #7	$70.85	13.329%	$80.2936	$80.29	$80.30	$80.30
7 purchase totals =	$779.31		$859.9405	$859.95	$860.00	$860.00