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	$222.45	3.567%	$230.3848	$230.38	$230.40	$230.40
Purchase #2	$145.88	13.799%	$166.01	$166.01	$166.00	$166.00
Purchase #3	$136.56	13.711%	$155.2837	$155.28	$155.30	$155.30
Purchase #4	$66.43	9.226%	$72.5588	$72.56	$72.55	$72.60
Purchase #5	$158.30	5.813%	$167.502	$167.50	$167.50	$167.50
Purchase #6	$46.35	6.748%	$49.4777	$49.48	$49.50	$49.50
Purchase #7	$99.29	3.287%	$102.5537	$102.55	$102.55	$102.60
7 purchase totals =	$875.26		$943.7707	$943.76	$943.80	$943.90