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	$137.27	10.698%	$151.9551	$151.96	$151.95	$152.00
Purchase #2	$72.99	7.282%	$78.3051	$78.31	$78.30	$78.30
Purchase #3	$69.87	4.169%	$72.7829	$72.78	$72.80	$72.80
Purchase #4	$135.64	13.513%	$153.969	$153.97	$153.95	$154.00
Purchase #5	$33.70	9.616%	$36.9406	$36.94	$36.95	$36.90
Purchase #6	$78.82	13.105%	$89.1494	$89.15	$89.15	$89.10
Purchase #7	$227.79	4.631%	$238.339	$238.34	$238.35	$238.30
7 purchase totals =	$756.08		$821.4411	$821.45	$821.45	$821.40