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	$231.48	11.419%	$257.9127	$257.91	$257.90	$257.90
Purchase #2	$100.84	4.565%	$105.4433	$105.44	$105.45	$105.40
Purchase #3	$121.90	3.741%	$126.4603	$126.46	$126.45	$126.50
Purchase #4	$199.42	12.126%	$223.6017	$223.60	$223.60	$223.60
Purchase #5	$203.39	10.515%	$224.7765	$224.78	$224.80	$224.80
Purchase #6	$89.77	6.103%	$95.2487	$95.25	$95.25	$95.20
Purchase #7	$16.41	13.346%	$18.6001	$18.60	$18.60	$18.60
7 purchase totals =	$963.21		$1,052.0433	$1,052.04	$1,052.05	$1,052.00