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	$106.72	5.176%	$112.2438	$112.24	$112.25	$112.20
Purchase #2	$59.98	7.102%	$64.2398	$64.24	$64.25	$64.20
Purchase #3	$62.49	12.232%	$70.1338	$70.13	$70.15	$70.10
Purchase #4	$209.67	4.656%	$219.4322	$219.43	$219.45	$219.40
Purchase #5	$160.66	13.516%	$182.3748	$182.37	$182.35	$182.40
Purchase #6	$185.77	9.566%	$203.5408	$203.54	$203.55	$203.50
Purchase #7	$129.42	12.443%	$145.5237	$145.52	$145.50	$145.50
7 purchase totals =	$914.71		$997.4889	$997.47	$997.50	$997.30