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	$209.64	8.422%	$227.2959	$227.30	$227.30	$227.30
Purchase #2	$95.76	7.856%	$103.2829	$103.28	$103.30	$103.30
Purchase #3	$240.62	6.322%	$255.832	$255.83	$255.85	$255.80
Purchase #4	$100.51	13.860%	$114.4407	$114.44	$114.45	$114.40
Purchase #5	$210.80	5.521%	$222.4383	$222.44	$222.45	$222.40
Purchase #6	$81.75	4.248%	$85.2227	$85.22	$85.20	$85.20
Purchase #7	$225.89	4.638%	$236.3668	$236.37	$236.35	$236.40
7 purchase totals =	$1,164.97		$1,244.8793	$1,244.88	$1,244.90	$1,244.80