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	$223.45	13.506%	$253.6292	$253.63	$253.65	$253.60
Purchase #2	$118.48	10.808%	$131.2853	$131.29	$131.30	$131.30
Purchase #3	$172.28	11.682%	$192.4057	$192.41	$192.40	$192.40
Purchase #4	$178.38	4.495%	$186.3982	$186.40	$186.40	$186.40
Purchase #5	$87.31	12.843%	$98.5232	$98.52	$98.50	$98.50
Purchase #6	$112.27	10.364%	$123.9057	$123.91	$123.90	$123.90
Purchase #7	$245.28	12.810%	$276.7004	$276.70	$276.70	$276.70
7 purchase totals =	$1,137.45		$1,262.8477	$1,262.86	$1,262.85	$1,262.80