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	$20.51	13.532%	$23.2854	$23.29	$23.30	$23.30
Purchase #2	$236.78	10.296%	$261.1589	$261.16	$261.15	$261.20
Purchase #3	$215.26	4.648%	$225.2653	$225.27	$225.25	$225.30
Purchase #4	$213.50	10.553%	$236.0307	$236.03	$236.05	$236.00
Purchase #5	$31.52	11.107%	$35.0209	$35.02	$35.00	$35.00
Purchase #6	$53.86	10.309%	$59.4124	$59.41	$59.40	$59.40
Purchase #7	$244.70	4.314%	$255.2564	$255.26	$255.25	$255.30
7 purchase totals =	$1,016.13		$1,095.4300	$1,095.44	$1,095.40	$1,095.50