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	$34.83	10.848%	$38.6084	$38.61	$38.60	$38.60
Purchase #2	$161.78	9.782%	$177.6053	$177.61	$177.60	$177.60
Purchase #3	$74.59	11.502%	$83.1693	$83.17	$83.15	$83.20
Purchase #4	$106.59	4.529%	$111.4175	$111.42	$111.40	$111.40
Purchase #5	$204.68	9.122%	$223.3509	$223.35	$223.35	$223.40
Purchase #6	$181.29	10.401%	$200.146	$200.15	$200.15	$200.10
Purchase #7	$35.54	8.524%	$38.5694	$38.57	$38.55	$38.60
7 purchase totals =	$799.30		$872.8668	$872.88	$872.80	$872.90