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	$186.45	11.745%	$208.3486	$208.35	$208.35	$208.30
Purchase #2	$222.52	7.178%	$238.4925	$238.49	$238.50	$238.50
Purchase #3	$49.71	9.772%	$54.5677	$54.57	$54.55	$54.60
Purchase #4	$143.29	9.627%	$157.0845	$157.08	$157.10	$157.10
Purchase #5	$53.96	13.802%	$61.4076	$61.41	$61.40	$61.40
Purchase #6	$122.80	12.814%	$138.5356	$138.54	$138.55	$138.50
Purchase #7	$83.68	10.465%	$92.4371	$92.44	$92.45	$92.40
7 purchase totals =	$862.41		$950.8736	$950.88	$950.90	$950.80