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	$57.67	13.413%	$65.4053	$65.41	$65.40	$65.40
Purchase #2	$114.38	12.560%	$128.7461	$128.75	$128.75	$128.70
Purchase #3	$195.54	12.447%	$219.8789	$219.88	$219.90	$219.90
Purchase #4	$14.49	5.405%	$15.2732	$15.27	$15.25	$15.30
Purchase #5	$103.52	8.271%	$112.0821	$112.08	$112.10	$112.10
Purchase #6	$144.57	6.425%	$153.8586	$153.86	$153.85	$153.90
Purchase #7	$124.76	5.239%	$131.2962	$131.30	$131.30	$131.30
7 purchase totals =	$754.93		$826.5404	$826.55	$826.55	$826.60