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	$132.54	12.187%	$148.6926	$148.69	$148.70	$148.70
Purchase #2	$48.98	7.525%	$52.6657	$52.67	$52.65	$52.70
Purchase #3	$44.59	8.620%	$48.4337	$48.43	$48.45	$48.40
Purchase #4	$130.95	6.325%	$139.2326	$139.23	$139.25	$139.20
Purchase #5	$94.58	8.487%	$102.607	$102.61	$102.60	$102.60
Purchase #6	$205.43	13.443%	$233.046	$233.05	$233.05	$233.00
Purchase #7	$139.40	12.141%	$156.3246	$156.32	$156.30	$156.30
7 purchase totals =	$796.47		$881.0022	$881.00	$881.00	$880.90