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	$164.39	9.663%	$180.275	$180.28	$180.30	$180.30
Purchase #2	$97.95	12.568%	$110.2604	$110.26	$110.25	$110.30
Purchase #3	$228.44	4.126%	$237.8654	$237.87	$237.85	$237.90
Purchase #4	$217.38	4.825%	$227.8686	$227.87	$227.85	$227.90
Purchase #5	$141.45	10.702%	$156.588	$156.59	$156.60	$156.60
Purchase #6	$144.56	5.738%	$152.8549	$152.85	$152.85	$152.90
Purchase #7	$30.73	5.311%	$32.3621	$32.36	$32.35	$32.40
7 purchase totals =	$1,024.90		$1,098.0744	$1,098.08	$1,098.05	$1,098.30