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	$43.54	9.496%	$47.6746	$47.67	$47.65	$47.70
Purchase #2	$36.76	5.732%	$38.8671	$38.87	$38.85	$38.90
Purchase #3	$153.29	12.542%	$172.5156	$172.52	$172.50	$172.50
Purchase #4	$240.33	3.138%	$247.8716	$247.87	$247.85	$247.90
Purchase #5	$12.46	5.499%	$13.1452	$13.15	$13.15	$13.10
Purchase #6	$29.70	7.307%	$31.8702	$31.87	$31.85	$31.90
Purchase #7	$181.77	10.124%	$200.1724	$200.17	$200.15	$200.20
7 purchase totals =	$697.85		$752.1167	$752.12	$752.00	$752.20