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	$139.61	10.489%	$154.2537	$154.25	$154.25	$154.30
Purchase #2	$158.88	6.772%	$169.6394	$169.64	$169.65	$169.60
Purchase #3	$87.93	13.255%	$99.5851	$99.59	$99.60	$99.60
Purchase #4	$141.38	5.722%	$149.4698	$149.47	$149.45	$149.50
Purchase #5	$6.67	10.445%	$7.3667	$7.37	$7.35	$7.40
Purchase #6	$73.81	9.252%	$80.6389	$80.64	$80.65	$80.60
Purchase #7	$40.74	4.444%	$42.5505	$42.55	$42.55	$42.60
7 purchase totals =	$649.02		$703.5041	$703.51	$703.50	$703.60