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	$164.81	12.429%	$185.2942	$185.29	$185.30	$185.30
Purchase #2	$193.88	3.452%	$200.5727	$200.57	$200.55	$200.60
Purchase #3	$131.52	12.527%	$147.9955	$148.00	$148.00	$148.00
Purchase #4	$135.72	12.376%	$152.5167	$152.52	$152.50	$152.50
Purchase #5	$95.92	8.821%	$104.3811	$104.38	$104.40	$104.40
Purchase #6	$233.93	4.608%	$244.7095	$244.71	$244.70	$244.70
Purchase #7	$232.56	10.694%	$257.43	$257.43	$257.45	$257.40
7 purchase totals =	$1,188.34		$1,292.8997	$1,292.90	$1,292.90	$1,292.90