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	$189.39	13.209%	$214.4065	$214.41	$214.40	$214.40
Purchase #2	$196.77	6.182%	$208.9343	$208.93	$208.95	$208.90
Purchase #3	$51.74	5.551%	$54.6121	$54.61	$54.60	$54.60
Purchase #4	$221.73	4.293%	$231.2489	$231.25	$231.25	$231.20
Purchase #5	$240.55	11.245%	$267.5998	$267.60	$267.60	$267.60
Purchase #6	$197.36	12.267%	$221.5702	$221.57	$221.55	$221.60
Purchase #7	$93.48	7.525%	$100.5144	$100.51	$100.50	$100.50
7 purchase totals =	$1,191.02		$1,298.8862	$1,298.88	$1,298.85	$1,298.80