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	$230.35	3.274%	$237.8917	$237.89	$237.90	$237.90
Purchase #2	$35.35	6.848%	$37.7708	$37.77	$37.75	$37.80
Purchase #3	$68.84	5.381%	$72.5443	$72.54	$72.55	$72.50
Purchase #4	$109.63	6.346%	$116.5871	$116.59	$116.60	$116.60
Purchase #5	$150.51	7.576%	$161.9126	$161.91	$161.90	$161.90
Purchase #6	$172.68	8.665%	$187.6427	$187.64	$187.65	$187.60
Purchase #7	$229.76	12.863%	$259.314	$259.31	$259.30	$259.30
7 purchase totals =	$997.12		$1,073.6632	$1,073.65	$1,073.65	$1,073.60