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	$219.63	3.657%	$227.6619	$227.66	$227.65	$227.70
Purchase #2	$247.29	13.200%	$279.9323	$279.93	$279.95	$279.90
Purchase #3	$42.65	6.487%	$45.4167	$45.42	$45.40	$45.40
Purchase #4	$66.91	3.528%	$69.2706	$69.27	$69.25	$69.30
Purchase #5	$206.92	3.142%	$213.4214	$213.42	$213.40	$213.40
Purchase #6	$103.30	9.523%	$113.1373	$113.14	$113.15	$113.10
Purchase #7	$220.32	12.488%	$247.8336	$247.83	$247.85	$247.80
7 purchase totals =	$1,107.02		$1,196.6738	$1,196.67	$1,196.65	$1,196.60