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	$59.30	3.872%	$61.5961	$61.60	$61.60	$61.60
Purchase #2	$31.79	3.640%	$32.9472	$32.95	$32.95	$32.90
Purchase #3	$149.74	5.617%	$158.1509	$158.15	$158.15	$158.20
Purchase #4	$101.71	13.428%	$115.3676	$115.37	$115.35	$115.40
Purchase #5	$243.78	7.574%	$262.2439	$262.24	$262.25	$262.20
Purchase #6	$42.46	7.640%	$45.7039	$45.70	$45.70	$45.70
Purchase #7	$164.93	5.855%	$174.5867	$174.59	$174.60	$174.60
7 purchase totals =	$793.71		$850.5963	$850.60	$850.60	$850.60