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	$121.37	11.123%	$134.87	$134.87	$134.85	$134.90
Purchase #2	$83.81	5.614%	$88.5151	$88.52	$88.50	$88.50
Purchase #3	$83.71	7.519%	$90.0042	$90.00	$90.00	$90.00
Purchase #4	$231.83	8.653%	$251.8902	$251.89	$251.90	$251.90
Purchase #5	$144.28	11.221%	$160.4697	$160.47	$160.45	$160.50
Purchase #6	$145.42	10.710%	$160.9945	$160.99	$161.00	$161.00
Purchase #7	$106.96	11.373%	$119.1246	$119.12	$119.10	$119.10
7 purchase totals =	$917.38		$1,005.8683	$1,005.86	$1,005.80	$1,005.90