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	$141.26	7.779%	$152.2486	$152.25	$152.25	$152.20
Purchase #2	$120.73	13.564%	$137.1058	$137.11	$137.10	$137.10
Purchase #3	$74.64	10.237%	$82.2809	$82.28	$82.30	$82.30
Purchase #4	$113.25	9.760%	$124.3032	$124.30	$124.30	$124.30
Purchase #5	$136.65	13.142%	$154.6085	$154.61	$154.60	$154.60
Purchase #6	$51.63	5.365%	$54.3999	$54.40	$54.40	$54.40
Purchase #7	$57.50	7.844%	$62.0103	$62.01	$62.00	$62.00
7 purchase totals =	$695.66		$766.9572	$766.96	$766.95	$766.90