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	$68.71	13.786%	$78.1824	$78.18	$78.20	$78.20
Purchase #2	$59.57	9.432%	$65.1886	$65.19	$65.20	$65.20
Purchase #3	$184.41	3.363%	$190.6117	$190.61	$190.60	$190.60
Purchase #4	$221.66	7.447%	$238.167	$238.17	$238.15	$238.20
Purchase #5	$217.31	5.153%	$228.508	$228.51	$228.50	$228.50
Purchase #6	$191.46	10.741%	$212.0247	$212.02	$212.00	$212.00
Purchase #7	$12.90	10.258%	$14.2233	$14.22	$14.20	$14.20
7 purchase totals =	$956.02		$1,026.9057	$1,026.90	$1,026.85	$1,026.90