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	$200.82	6.289%	$213.4496	$213.45	$213.45	$213.40
Purchase #2	$46.70	3.784%	$48.4671	$48.47	$48.45	$48.50
Purchase #3	$14.86	4.221%	$15.4872	$15.49	$15.50	$15.50
Purchase #4	$21.34	7.131%	$22.8618	$22.86	$22.85	$22.90
Purchase #5	$145.34	3.508%	$150.4385	$150.44	$150.45	$150.40
Purchase #6	$102.69	6.190%	$109.0465	$109.05	$109.05	$109.00
Purchase #7	$62.25	6.260%	$66.1469	$66.15	$66.15	$66.10
7 purchase totals =	$594.00		$625.8976	$625.91	$625.90	$625.80