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	$213.69	5.492%	$225.4259	$225.43	$225.45	$225.40
Purchase #2	$50.98	12.426%	$57.3148	$57.31	$57.30	$57.30
Purchase #3	$145.96	5.533%	$154.036	$154.04	$154.05	$154.00
Purchase #4	$215.95	6.317%	$229.5916	$229.59	$229.60	$229.60
Purchase #5	$216.48	5.173%	$227.6785	$227.68	$227.70	$227.70
Purchase #6	$86.60	4.827%	$90.7802	$90.78	$90.80	$90.80
Purchase #7	$74.83	7.643%	$80.5493	$80.55	$80.55	$80.50
7 purchase totals =	$1,004.49		$1,065.3763	$1,065.38	$1,065.45	$1,065.30