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	$240.37	5.237%	$252.9582	$252.96	$252.95	$253.00
Purchase #2	$158.85	10.110%	$174.9097	$174.91	$174.90	$174.90
Purchase #3	$82.75	10.792%	$91.6804	$91.68	$91.70	$91.70
Purchase #4	$90.71	13.652%	$103.0937	$103.09	$103.10	$103.10
Purchase #5	$140.71	8.455%	$152.607	$152.61	$152.60	$152.60
Purchase #6	$55.27	11.151%	$61.4332	$61.43	$61.45	$61.40
Purchase #7	$169.95	11.584%	$189.637	$189.64	$189.65	$189.60
7 purchase totals =	$938.61		$1,026.3192	$1,026.32	$1,026.35	$1,026.30