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	$205.79	9.573%	$225.4903	$225.49	$225.50	$225.50
Purchase #2	$184.66	10.698%	$204.4149	$204.41	$204.40	$204.40
Purchase #3	$46.27	5.686%	$48.9009	$48.90	$48.90	$48.90
Purchase #4	$44.73	7.829%	$48.2319	$48.23	$48.25	$48.20
Purchase #5	$73.35	12.264%	$82.3456	$82.35	$82.35	$82.30
Purchase #6	$184.89	11.375%	$205.9212	$205.92	$205.90	$205.90
Purchase #7	$207.55	3.594%	$215.0093	$215.01	$215.00	$215.00
7 purchase totals =	$947.24		$1,030.3141	$1,030.31	$1,030.30	$1,030.20