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	$127.88	3.726%	$132.6448	$132.64	$132.65	$132.60
Purchase #2	$216.36	4.262%	$225.5813	$225.58	$225.60	$225.60
Purchase #3	$151.32	11.239%	$168.3269	$168.33	$168.35	$168.30
Purchase #4	$142.82	5.676%	$150.9265	$150.93	$150.95	$150.90
Purchase #5	$92.45	5.682%	$97.703	$97.70	$97.70	$97.70
Purchase #6	$154.88	6.751%	$165.3359	$165.34	$165.35	$165.30
Purchase #7	$155.56	8.647%	$169.0113	$169.01	$169.00	$169.00
7 purchase totals =	$1,041.27		$1,109.5297	$1,109.53	$1,109.60	$1,109.40