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	$211.92	11.858%	$237.0495	$237.05	$237.05	$237.00
Purchase #2	$205.59	8.587%	$223.244	$223.24	$223.25	$223.20
Purchase #3	$9.78	4.597%	$10.2296	$10.23	$10.25	$10.20
Purchase #4	$151.64	13.779%	$172.5345	$172.53	$172.55	$172.50
Purchase #5	$112.71	3.426%	$116.5714	$116.57	$116.55	$116.60
Purchase #6	$144.54	4.732%	$151.3796	$151.38	$151.40	$151.40
Purchase #7	$178.68	12.119%	$200.3342	$200.33	$200.35	$200.30
7 purchase totals =	$1,014.86		$1,111.3428	$1,111.33	$1,111.40	$1,111.20