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	$104.43	11.395%	$116.3298	$116.33	$116.35	$116.30
Purchase #2	$129.73	9.731%	$142.354	$142.35	$142.35	$142.40
Purchase #3	$228.53	11.702%	$255.2726	$255.27	$255.25	$255.30
Purchase #4	$229.32	4.257%	$239.0822	$239.08	$239.10	$239.10
Purchase #5	$85.84	4.208%	$89.4521	$89.45	$89.45	$89.50
Purchase #6	$47.67	12.222%	$53.4962	$53.50	$53.50	$53.50
Purchase #7	$130.95	3.466%	$135.4887	$135.49	$135.50	$135.50
7 purchase totals =	$956.47		$1,031.4756	$1,031.47	$1,031.50	$1,031.60