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	$230.39	10.168%	$253.8161	$253.82	$253.80	$253.80
Purchase #2	$49.71	8.346%	$53.8588	$53.86	$53.85	$53.90
Purchase #3	$222.28	8.207%	$240.5225	$240.52	$240.50	$240.50
Purchase #4	$84.51	12.311%	$94.914	$94.91	$94.90	$94.90
Purchase #5	$20.30	5.748%	$21.4668	$21.47	$21.45	$21.50
Purchase #6	$244.33	4.730%	$255.8868	$255.89	$255.90	$255.90
Purchase #7	$184.53	11.556%	$205.8543	$205.85	$205.85	$205.90
7 purchase totals =	$1,036.05		$1,126.3193	$1,126.32	$1,126.25	$1,126.40