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	$126.96	9.762%	$139.3538	$139.35	$139.35	$139.40
Purchase #2	$167.73	13.231%	$189.9224	$189.92	$189.90	$189.90
Purchase #3	$54.31	5.383%	$57.2335	$57.23	$57.25	$57.20
Purchase #4	$111.28	5.803%	$117.7376	$117.74	$117.75	$117.70
Purchase #5	$179.90	13.320%	$203.8627	$203.86	$203.85	$203.90
Purchase #6	$117.53	8.320%	$127.3085	$127.31	$127.30	$127.30
Purchase #7	$201.50	7.125%	$215.8569	$215.86	$215.85	$215.90
7 purchase totals =	$959.21		$1,051.2754	$1,051.27	$1,051.25	$1,051.30