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	$75.50	10.754%	$83.6193	$83.62	$83.60	$83.60
Purchase #2	$230.28	11.577%	$256.9395	$256.94	$256.95	$256.90
Purchase #3	$233.57	9.743%	$256.3267	$256.33	$256.35	$256.30
Purchase #4	$74.72	4.710%	$78.2393	$78.24	$78.25	$78.20
Purchase #5	$239.99	9.676%	$263.2114	$263.21	$263.20	$263.20
Purchase #6	$91.54	11.823%	$102.3628	$102.36	$102.35	$102.40
Purchase #7	$55.29	5.650%	$58.4139	$58.41	$58.40	$58.40
7 purchase totals =	$1,000.89		$1,099.1129	$1,099.11	$1,099.10	$1,099.00