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	$194.86	5.539%	$205.6533	$205.65	$205.65	$205.70
Purchase #2	$29.30	7.335%	$31.4492	$31.45	$31.45	$31.40
Purchase #3	$151.75	10.222%	$167.2619	$167.26	$167.25	$167.30
Purchase #4	$248.57	5.361%	$261.8958	$261.90	$261.90	$261.90
Purchase #5	$99.30	3.580%	$102.8549	$102.85	$102.85	$102.90
Purchase #6	$115.95	13.587%	$131.7041	$131.70	$131.70	$131.70
Purchase #7	$50.61	10.316%	$55.8309	$55.83	$55.85	$55.80
7 purchase totals =	$890.34		$956.6501	$956.64	$956.65	$956.70