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	$214.57	11.110%	$238.4087	$238.41	$238.40	$238.40
Purchase #2	$131.90	10.182%	$145.3301	$145.33	$145.35	$145.30
Purchase #3	$212.29	5.149%	$223.2208	$223.22	$223.20	$223.20
Purchase #4	$135.78	4.140%	$141.4013	$141.40	$141.40	$141.40
Purchase #5	$57.85	13.779%	$65.8212	$65.82	$65.80	$65.80
Purchase #6	$53.88	6.847%	$57.5692	$57.57	$57.55	$57.60
Purchase #7	$163.35	3.243%	$168.6474	$168.65	$168.65	$168.60
7 purchase totals =	$969.62		$1,040.3987	$1,040.40	$1,040.35	$1,040.30