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	$192.54	3.755%	$199.7699	$199.77	$199.75	$199.80
Purchase #2	$153.81	6.179%	$163.3139	$163.31	$163.30	$163.30
Purchase #3	$111.33	10.645%	$123.1811	$123.18	$123.20	$123.20
Purchase #4	$89.42	12.249%	$100.3731	$100.37	$100.35	$100.40
Purchase #5	$72.26	11.230%	$80.3748	$80.37	$80.35	$80.40
Purchase #6	$209.33	3.853%	$217.3955	$217.40	$217.40	$217.40
Purchase #7	$190.75	12.190%	$214.0024	$214.00	$214.00	$214.00
7 purchase totals =	$1,019.44		$1,098.4107	$1,098.40	$1,098.35	$1,098.50