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	$208.84	7.191%	$223.8577	$223.86	$223.85	$223.90
Purchase #2	$242.56	5.748%	$256.5023	$256.50	$256.50	$256.50
Purchase #3	$182.59	13.520%	$207.2762	$207.28	$207.30	$207.30
Purchase #4	$39.55	5.186%	$41.6011	$41.60	$41.60	$41.60
Purchase #5	$203.32	6.108%	$215.7388	$215.74	$215.75	$215.70
Purchase #6	$18.36	3.187%	$18.9451	$18.95	$18.95	$18.90
Purchase #7	$35.34	8.567%	$38.3676	$38.37	$38.35	$38.40
7 purchase totals =	$930.56		$1,002.2888	$1,002.30	$1,002.30	$1,002.30