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	$135.54	13.592%	$153.9626	$153.96	$153.95	$154.00
Purchase #2	$94.31	8.273%	$102.1123	$102.11	$102.10	$102.10
Purchase #3	$195.89	13.348%	$222.0374	$222.04	$222.05	$222.00
Purchase #4	$142.62	5.776%	$150.8577	$150.86	$150.85	$150.90
Purchase #5	$169.89	10.827%	$188.284	$188.28	$188.30	$188.30
Purchase #6	$201.43	3.481%	$208.4418	$208.44	$208.45	$208.40
Purchase #7	$233.87	12.281%	$262.5916	$262.59	$262.60	$262.60
7 purchase totals =	$1,173.55		$1,288.2874	$1,288.28	$1,288.30	$1,288.30