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	$41.99	7.569%	$45.1682	$45.17	$45.15	$45.20
Purchase #2	$164.94	3.853%	$171.2951	$171.30	$171.30	$171.30
Purchase #3	$116.52	4.520%	$121.7867	$121.79	$121.80	$121.80
Purchase #4	$37.46	11.425%	$41.7398	$41.74	$41.75	$41.70
Purchase #5	$39.47	7.401%	$42.3912	$42.39	$42.40	$42.40
Purchase #6	$11.61	11.476%	$12.9424	$12.94	$12.95	$12.90
Purchase #7	$157.30	4.407%	$164.2322	$164.23	$164.25	$164.20
7 purchase totals =	$569.29		$599.5556	$599.56	$599.60	$599.50