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	$245.59	4.670%	$257.0591	$257.06	$257.05	$257.10
Purchase #2	$104.55	11.812%	$116.8994	$116.90	$116.90	$116.90
Purchase #3	$55.60	6.153%	$59.0211	$59.02	$59.00	$59.00
Purchase #4	$72.74	10.515%	$80.3886	$80.39	$80.40	$80.40
Purchase #5	$96.92	6.738%	$103.4505	$103.45	$103.45	$103.50
Purchase #6	$94.92	12.428%	$106.7167	$106.72	$106.70	$106.70
Purchase #7	$30.92	6.538%	$32.9415	$32.94	$32.95	$32.90
7 purchase totals =	$701.24		$756.4769	$756.48	$756.45	$756.50