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	$194.80	5.295%	$205.1147	$205.11	$205.10	$205.10
Purchase #2	$176.48	11.222%	$196.2846	$196.28	$196.30	$196.30
Purchase #3	$105.65	7.419%	$113.4882	$113.49	$113.50	$113.50
Purchase #4	$38.43	5.820%	$40.6666	$40.67	$40.65	$40.70
Purchase #5	$178.75	9.868%	$196.3891	$196.39	$196.40	$196.40
Purchase #6	$106.63	11.381%	$118.7656	$118.77	$118.75	$118.80
Purchase #7	$83.32	12.126%	$93.4234	$93.42	$93.40	$93.40
7 purchase totals =	$884.06		$964.1322	$964.13	$964.10	$964.20