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	$224.46	11.354%	$249.9452	$249.95	$249.95	$249.90
Purchase #2	$226.42	12.320%	$254.3149	$254.31	$254.30	$254.30
Purchase #3	$79.54	13.292%	$90.1125	$90.11	$90.10	$90.10
Purchase #4	$80.27	13.292%	$90.9395	$90.94	$90.95	$90.90
Purchase #5	$163.85	12.654%	$184.5836	$184.58	$184.60	$184.60
Purchase #6	$209.42	3.779%	$217.334	$217.33	$217.35	$217.30
Purchase #7	$185.61	10.776%	$205.6113	$205.61	$205.60	$205.60
7 purchase totals =	$1,169.57		$1,292.8410	$1,292.83	$1,292.85	$1,292.70