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	$32.49	3.630%	$33.6694	$33.67	$33.65	$33.70
Purchase #2	$38.33	10.107%	$42.204	$42.20	$42.20	$42.20
Purchase #3	$51.89	9.370%	$56.7521	$56.75	$56.75	$56.80
Purchase #4	$27.45	10.578%	$30.3537	$30.35	$30.35	$30.40
Purchase #5	$117.57	12.786%	$132.6025	$132.60	$132.60	$132.60
Purchase #6	$179.78	3.136%	$185.4179	$185.42	$185.40	$185.40
Purchase #7	$247.44	6.440%	$263.3751	$263.38	$263.40	$263.40
7 purchase totals =	$694.95		$744.3747	$744.37	$744.35	$744.50