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	$241.89	11.586%	$269.9154	$269.92	$269.90	$269.90
Purchase #2	$114.31	3.801%	$118.6549	$118.65	$118.65	$118.70
Purchase #3	$98.30	13.345%	$111.4181	$111.42	$111.40	$111.40
Purchase #4	$54.47	3.504%	$56.3786	$56.38	$56.40	$56.40
Purchase #5	$223.57	11.555%	$249.4035	$249.40	$249.40	$249.40
Purchase #6	$153.27	5.598%	$161.8501	$161.85	$161.85	$161.90
Purchase #7	$16.73	9.671%	$18.348	$18.35	$18.35	$18.30
7 purchase totals =	$902.54		$985.9686	$985.97	$985.95	$986.00