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	$190.77	5.113%	$200.5241	$200.52	$200.50	$200.50
Purchase #2	$234.31	5.383%	$246.9229	$246.92	$246.90	$246.90
Purchase #3	$6.53	10.571%	$7.2203	$7.22	$7.20	$7.20
Purchase #4	$11.80	13.597%	$13.4044	$13.40	$13.40	$13.40
Purchase #5	$40.75	11.289%	$45.3503	$45.35	$45.35	$45.40
Purchase #6	$164.74	11.368%	$183.4676	$183.47	$183.45	$183.50
Purchase #7	$135.47	4.724%	$141.8696	$141.87	$141.85	$141.90
7 purchase totals =	$784.37		$838.7592	$838.75	$838.65	$838.80