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	$200.32	10.509%	$221.3716	$221.37	$221.35	$221.40
Purchase #2	$65.81	10.458%	$72.6924	$72.69	$72.70	$72.70
Purchase #3	$130.50	13.277%	$147.8265	$147.83	$147.85	$147.80
Purchase #4	$64.71	8.468%	$70.1896	$70.19	$70.20	$70.20
Purchase #5	$119.28	6.650%	$127.2121	$127.21	$127.20	$127.20
Purchase #6	$145.66	12.778%	$164.2724	$164.27	$164.25	$164.30
Purchase #7	$76.48	7.839%	$82.4753	$82.48	$82.50	$82.50
7 purchase totals =	$802.76		$886.0399	$886.04	$886.05	$886.10