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	$62.56	4.183%	$65.1769	$65.18	$65.20	$65.20
Purchase #2	$101.53	9.716%	$111.3947	$111.39	$111.40	$111.40
Purchase #3	$18.80	12.863%	$21.2182	$21.22	$21.20	$21.20
Purchase #4	$59.38	3.728%	$61.5937	$61.59	$61.60	$61.60
Purchase #5	$27.47	10.354%	$30.3142	$30.31	$30.30	$30.30
Purchase #6	$56.41	5.176%	$59.3298	$59.33	$59.35	$59.30
Purchase #7	$11.58	10.226%	$12.7642	$12.76	$12.75	$12.80
7 purchase totals =	$337.73		$361.7917	$361.78	$361.80	$361.80