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	$49.83	13.332%	$56.4733	$56.47	$56.45	$56.50
Purchase #2	$169.83	6.151%	$180.2762	$180.28	$180.30	$180.30
Purchase #3	$31.66	11.235%	$35.217	$35.22	$35.20	$35.20
Purchase #4	$228.38	12.824%	$257.6675	$257.67	$257.65	$257.70
Purchase #5	$245.73	7.763%	$264.806	$264.81	$264.80	$264.80
Purchase #6	$162.61	10.721%	$180.0434	$180.04	$180.05	$180.00
Purchase #7	$38.30	12.442%	$43.0653	$43.07	$43.05	$43.10
7 purchase totals =	$926.34		$1,017.5487	$1,017.56	$1,017.50	$1,017.60