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	$230.36	8.330%	$249.549	$249.55	$249.55	$249.50
Purchase #2	$177.72	10.765%	$196.8516	$196.85	$196.85	$196.90
Purchase #3	$144.39	9.780%	$158.5113	$158.51	$158.50	$158.50
Purchase #4	$104.38	7.679%	$112.3953	$112.40	$112.40	$112.40
Purchase #5	$96.92	5.329%	$102.0849	$102.08	$102.10	$102.10
Purchase #6	$156.51	8.776%	$170.2453	$170.25	$170.25	$170.20
Purchase #7	$69.39	3.370%	$71.7284	$71.73	$71.75	$71.70
7 purchase totals =	$979.67		$1,061.3658	$1,061.37	$1,061.40	$1,061.30