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	$153.66	13.630%	$174.6039	$174.60	$174.60	$174.60
Purchase #2	$234.96	8.731%	$255.4744	$255.47	$255.45	$255.50
Purchase #3	$239.79	9.377%	$262.2751	$262.28	$262.30	$262.30
Purchase #4	$79.82	8.291%	$86.4379	$86.44	$86.45	$86.40
Purchase #5	$120.81	7.871%	$130.319	$130.32	$130.30	$130.30
Purchase #6	$167.58	4.144%	$174.5245	$174.52	$174.50	$174.50
Purchase #7	$5.55	5.445%	$5.8522	$5.85	$5.85	$5.90
7 purchase totals =	$1,002.17		$1,089.4870	$1,089.48	$1,089.45	$1,089.50