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	$240.40	10.479%	$265.5915	$265.59	$265.60	$265.60
Purchase #2	$208.55	10.239%	$229.9034	$229.90	$229.90	$229.90
Purchase #3	$31.56	4.482%	$32.9745	$32.97	$32.95	$33.00
Purchase #4	$157.34	6.345%	$167.3232	$167.32	$167.30	$167.30
Purchase #5	$85.77	4.672%	$89.7772	$89.78	$89.80	$89.80
Purchase #6	$127.88	7.613%	$137.6155	$137.62	$137.60	$137.60
Purchase #7	$151.41	9.517%	$165.8197	$165.82	$165.80	$165.80
7 purchase totals =	$1,002.91		$1,089.0050	$1,089.00	$1,088.95	$1,089.00