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	$64.76	4.191%	$67.4741	$67.47	$67.45	$67.50
Purchase #2	$136.54	5.372%	$143.8749	$143.87	$143.85	$143.90
Purchase #3	$213.55	5.498%	$225.291	$225.29	$225.30	$225.30
Purchase #4	$12.39	10.161%	$13.6489	$13.65	$13.65	$13.60
Purchase #5	$238.32	11.482%	$265.6839	$265.68	$265.70	$265.70
Purchase #6	$21.33	13.635%	$24.2383	$24.24	$24.25	$24.20
Purchase #7	$233.60	12.286%	$262.3001	$262.30	$262.30	$262.30
7 purchase totals =	$920.49		$1,002.5112	$1,002.50	$1,002.50	$1,002.50