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	$239.81	7.356%	$257.4504	$257.45	$257.45	$257.50
Purchase #2	$91.42	6.661%	$97.5095	$97.51	$97.50	$97.50
Purchase #3	$184.85	6.212%	$196.3329	$196.33	$196.35	$196.30
Purchase #4	$36.60	11.629%	$40.8562	$40.86	$40.85	$40.90
Purchase #5	$57.99	4.111%	$60.374	$60.37	$60.35	$60.40
Purchase #6	$162.64	6.358%	$172.9807	$172.98	$173.00	$173.00
Purchase #7	$227.91	9.403%	$249.3404	$249.34	$249.35	$249.30
7 purchase totals =	$1,001.22		$1,074.8441	$1,074.84	$1,074.85	$1,074.90