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	$95.40	13.716%	$108.4851	$108.49	$108.50	$108.50
Purchase #2	$132.36	7.237%	$141.9389	$141.94	$141.95	$141.90
Purchase #3	$238.86	11.363%	$266.0017	$266.00	$266.00	$266.00
Purchase #4	$93.53	13.288%	$105.9583	$105.96	$105.95	$106.00
Purchase #5	$135.33	9.560%	$148.2675	$148.27	$148.25	$148.30
Purchase #6	$155.70	13.231%	$176.3007	$176.30	$176.30	$176.30
Purchase #7	$105.56	5.498%	$111.3637	$111.36	$111.35	$111.40
7 purchase totals =	$956.74		$1,058.3159	$1,058.32	$1,058.30	$1,058.40