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	$238.57	10.260%	$263.0473	$263.05	$263.05	$263.00
Purchase #2	$213.71	13.668%	$242.9199	$242.92	$242.90	$242.90
Purchase #3	$20.62	6.181%	$21.8945	$21.89	$21.90	$21.90
Purchase #4	$34.77	11.616%	$38.8089	$38.81	$38.80	$38.80
Purchase #5	$119.64	3.456%	$123.7748	$123.77	$123.75	$123.80
Purchase #6	$55.56	9.345%	$60.7521	$60.75	$60.75	$60.80
Purchase #7	$193.52	12.641%	$217.9829	$217.98	$218.00	$218.00
7 purchase totals =	$876.39		$969.1804	$969.17	$969.15	$969.20