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	$226.70	12.750%	$255.6043	$255.60	$255.60	$255.60
Purchase #2	$59.64	10.510%	$65.9082	$65.91	$65.90	$65.90
Purchase #3	$169.83	5.346%	$178.9091	$178.91	$178.90	$178.90
Purchase #4	$205.86	13.684%	$234.0299	$234.03	$234.05	$234.00
Purchase #5	$20.49	5.853%	$21.6893	$21.69	$21.70	$21.70
Purchase #6	$166.54	9.835%	$182.9192	$182.92	$182.90	$182.90
Purchase #7	$209.60	9.389%	$229.2793	$229.28	$229.30	$229.30
7 purchase totals =	$1,058.66		$1,168.3393	$1,168.34	$1,168.35	$1,168.30