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	$76.31	8.525%	$82.8154	$82.82	$82.80	$82.80
Purchase #2	$239.30	5.844%	$253.2847	$253.28	$253.30	$253.30
Purchase #3	$150.27	9.788%	$164.9784	$164.98	$165.00	$165.00
Purchase #4	$109.32	7.349%	$117.3539	$117.35	$117.35	$117.40
Purchase #5	$207.76	9.635%	$227.7777	$227.78	$227.80	$227.80
Purchase #6	$57.27	5.244%	$60.2732	$60.27	$60.25	$60.30
Purchase #7	$135.86	11.525%	$151.5179	$151.52	$151.50	$151.50
7 purchase totals =	$976.09		$1,058.0012	$1,058.00	$1,058.00	$1,058.10