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	$215.55	4.681%	$225.6399	$225.64	$225.65	$225.60
Purchase #2	$181.48	9.252%	$198.2705	$198.27	$198.25	$198.30
Purchase #3	$191.38	13.712%	$217.622	$217.62	$217.60	$217.60
Purchase #4	$40.50	12.343%	$45.4989	$45.50	$45.50	$45.50
Purchase #5	$10.25	6.499%	$10.9161	$10.92	$10.90	$10.90
Purchase #6	$35.80	6.136%	$37.9967	$38.00	$38.00	$38.00
Purchase #7	$100.41	10.474%	$110.9269	$110.93	$110.95	$110.90
7 purchase totals =	$775.37		$846.8710	$846.88	$846.85	$846.80