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	$217.56	13.493%	$246.9154	$246.92	$246.90	$246.90
Purchase #2	$233.53	12.840%	$263.5153	$263.52	$263.50	$263.50
Purchase #3	$130.34	6.854%	$139.2735	$139.27	$139.25	$139.30
Purchase #4	$124.28	3.361%	$128.4571	$128.46	$128.45	$128.50
Purchase #5	$75.69	12.653%	$85.2671	$85.27	$85.25	$85.30
Purchase #6	$239.90	5.393%	$252.8378	$252.84	$252.85	$252.80
Purchase #7	$59.39	10.140%	$65.4121	$65.41	$65.40	$65.40
7 purchase totals =	$1,080.69		$1,181.6783	$1,181.69	$1,181.60	$1,181.70