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	$211.84	4.660%	$221.7117	$221.71	$221.70	$221.70
Purchase #2	$194.36	10.303%	$214.3849	$214.38	$214.40	$214.40
Purchase #3	$52.83	12.426%	$59.3947	$59.39	$59.40	$59.40
Purchase #4	$246.59	3.647%	$255.5831	$255.58	$255.60	$255.60
Purchase #5	$141.71	10.531%	$156.6335	$156.63	$156.65	$156.60
Purchase #6	$142.42	10.107%	$156.8144	$156.81	$156.80	$156.80
Purchase #7	$7.68	8.432%	$8.3276	$8.33	$8.35	$8.30
7 purchase totals =	$997.43		$1,072.8499	$1,072.83	$1,072.90	$1,072.80