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	$96.70	12.137%	$108.4365	$108.44	$108.45	$108.40
Purchase #2	$171.81	13.361%	$194.7655	$194.77	$194.75	$194.80
Purchase #3	$59.25	12.526%	$66.6717	$66.67	$66.65	$66.70
Purchase #4	$227.31	9.853%	$249.7069	$249.71	$249.70	$249.70
Purchase #5	$68.92	4.865%	$72.273	$72.27	$72.25	$72.30
Purchase #6	$198.58	5.109%	$208.7255	$208.73	$208.75	$208.70
Purchase #7	$190.25	5.343%	$200.4151	$200.42	$200.40	$200.40
7 purchase totals =	$1,012.82		$1,100.9942	$1,101.01	$1,100.95	$1,101.00