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	$111.31	4.853%	$116.7119	$116.71	$116.70	$116.70
Purchase #2	$155.51	6.682%	$165.9012	$165.90	$165.90	$165.90
Purchase #3	$209.57	3.547%	$217.0034	$217.00	$217.00	$217.00
Purchase #4	$221.27	8.261%	$239.5491	$239.55	$239.55	$239.50
Purchase #5	$132.76	9.221%	$145.0018	$145.00	$145.00	$145.00
Purchase #6	$93.32	12.475%	$104.9617	$104.96	$104.95	$105.00
Purchase #7	$83.82	6.846%	$89.5583	$89.56	$89.55	$89.60
7 purchase totals =	$1,007.56		$1,078.6874	$1,078.68	$1,078.65	$1,078.70