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	$126.74	8.619%	$137.6637	$137.66	$137.65	$137.70
Purchase #2	$109.70	13.723%	$124.7541	$124.75	$124.75	$124.80
Purchase #3	$90.54	11.834%	$101.2545	$101.25	$101.25	$101.30
Purchase #4	$215.84	10.323%	$238.1212	$238.12	$238.10	$238.10
Purchase #5	$84.46	13.618%	$95.9618	$95.96	$95.95	$96.00
Purchase #6	$150.79	12.335%	$169.3899	$169.39	$169.40	$169.40
Purchase #7	$226.57	5.303%	$238.585	$238.59	$238.60	$238.60
7 purchase totals =	$1,004.64		$1,105.7302	$1,105.72	$1,105.70	$1,105.90