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	$164.45	5.503%	$173.4997	$173.50	$173.50	$173.50
Purchase #2	$18.92	12.341%	$21.2549	$21.25	$21.25	$21.30
Purchase #3	$113.25	10.615%	$125.2715	$125.27	$125.25	$125.30
Purchase #4	$112.55	13.184%	$127.3886	$127.39	$127.40	$127.40
Purchase #5	$19.82	6.781%	$21.164	$21.16	$21.15	$21.20
Purchase #6	$97.85	12.294%	$109.8797	$109.88	$109.90	$109.90
Purchase #7	$180.27	4.851%	$189.0149	$189.01	$189.00	$189.00
7 purchase totals =	$707.11		$767.4733	$767.46	$767.45	$767.60