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	$149.86	9.550%	$164.1716	$164.17	$164.15	$164.20
Purchase #2	$137.48	10.515%	$151.936	$151.94	$151.95	$151.90
Purchase #3	$217.77	8.338%	$235.9277	$235.93	$235.95	$235.90
Purchase #4	$12.25	5.119%	$12.8771	$12.88	$12.90	$12.90
Purchase #5	$148.26	5.800%	$156.8591	$156.86	$156.85	$156.90
Purchase #6	$28.81	12.620%	$32.4458	$32.45	$32.45	$32.40
Purchase #7	$159.33	7.321%	$170.9945	$170.99	$171.00	$171.00
7 purchase totals =	$853.76		$925.2118	$925.22	$925.25	$925.20