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	$231.65	3.292%	$239.2759	$239.28	$239.30	$239.30
Purchase #2	$10.36	10.775%	$11.4763	$11.48	$11.50	$11.50
Purchase #3	$196.70	6.517%	$209.5189	$209.52	$209.50	$209.50
Purchase #4	$70.56	3.146%	$72.7798	$72.78	$72.80	$72.80
Purchase #5	$134.30	7.650%	$144.574	$144.57	$144.55	$144.60
Purchase #6	$132.33	5.505%	$139.6148	$139.61	$139.60	$139.60
Purchase #7	$171.59	10.572%	$189.7305	$189.73	$189.75	$189.70
7 purchase totals =	$947.49		$1,006.9702	$1,006.97	$1,007.00	$1,007.00