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	$56.73	8.444%	$61.5203	$61.52	$61.50	$61.50
Purchase #2	$37.25	8.339%	$40.3563	$40.36	$40.35	$40.40
Purchase #3	$220.64	3.864%	$229.1655	$229.17	$229.15	$229.20
Purchase #4	$38.27	8.324%	$41.4556	$41.46	$41.45	$41.50
Purchase #5	$231.37	12.502%	$260.2959	$260.30	$260.30	$260.30
Purchase #6	$232.93	10.868%	$258.2448	$258.24	$258.25	$258.20
Purchase #7	$153.77	9.783%	$168.8133	$168.81	$168.80	$168.80
7 purchase totals =	$970.96		$1,059.8517	$1,059.86	$1,059.80	$1,059.90