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	$125.74	4.390%	$131.26	$131.26	$131.25	$131.30
Purchase #2	$177.86	10.488%	$196.514	$196.51	$196.50	$196.50
Purchase #3	$39.73	13.445%	$45.0717	$45.07	$45.05	$45.10
Purchase #4	$48.73	10.610%	$53.9003	$53.90	$53.90	$53.90
Purchase #5	$16.92	10.518%	$18.6996	$18.70	$18.70	$18.70
Purchase #6	$115.60	13.648%	$131.3771	$131.38	$131.40	$131.40
Purchase #7	$16.72	9.772%	$18.3539	$18.35	$18.35	$18.40
7 purchase totals =	$541.30		$595.1766	$595.17	$595.15	$595.30