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	$241.98	4.708%	$253.3724	$253.37	$253.35	$253.40
Purchase #2	$200.74	11.503%	$223.8311	$223.83	$223.85	$223.80
Purchase #3	$16.93	9.379%	$18.5179	$18.52	$18.50	$18.50
Purchase #4	$126.40	11.440%	$140.8602	$140.86	$140.85	$140.90
Purchase #5	$249.86	10.235%	$275.4332	$275.43	$275.45	$275.40
Purchase #6	$48.87	12.128%	$54.797	$54.80	$54.80	$54.80
Purchase #7	$166.81	6.550%	$177.7361	$177.74	$177.75	$177.70
7 purchase totals =	$1,051.59		$1,144.5479	$1,144.55	$1,144.55	$1,144.50