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	$162.87	6.762%	$173.8833	$173.88	$173.90	$173.90
Purchase #2	$120.85	3.221%	$124.7426	$124.74	$124.75	$124.70
Purchase #3	$112.92	5.820%	$119.4919	$119.49	$119.50	$119.50
Purchase #4	$227.42	5.673%	$240.3215	$240.32	$240.30	$240.30
Purchase #5	$214.69	4.820%	$225.0381	$225.04	$225.05	$225.00
Purchase #6	$105.32	6.763%	$112.4428	$112.44	$112.45	$112.40
Purchase #7	$41.65	4.817%	$43.6563	$43.66	$43.65	$43.70
7 purchase totals =	$985.72		$1,039.5765	$1,039.57	$1,039.60	$1,039.50