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	$209.53	10.497%	$231.5244	$231.52	$231.50	$231.50
Purchase #2	$78.71	4.135%	$81.9647	$81.96	$81.95	$82.00
Purchase #3	$200.47	11.531%	$223.5862	$223.59	$223.60	$223.60
Purchase #4	$210.55	7.749%	$226.8655	$226.87	$226.85	$226.90
Purchase #5	$134.92	13.632%	$153.3123	$153.31	$153.30	$153.30
Purchase #6	$244.61	6.123%	$259.5875	$259.59	$259.60	$259.60
Purchase #7	$195.93	6.851%	$209.3532	$209.35	$209.35	$209.40
7 purchase totals =	$1,274.72		$1,386.1938	$1,386.19	$1,386.15	$1,386.30