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	$100.83	11.206%	$112.129	$112.13	$112.15	$112.10
Purchase #2	$207.90	3.453%	$215.0788	$215.08	$215.10	$215.10
Purchase #3	$203.43	11.386%	$226.5925	$226.59	$226.60	$226.60
Purchase #4	$162.88	3.648%	$168.8219	$168.82	$168.80	$168.80
Purchase #5	$245.78	3.830%	$255.1934	$255.19	$255.20	$255.20
Purchase #6	$122.98	7.399%	$132.0793	$132.08	$132.10	$132.10
Purchase #7	$45.62	10.692%	$50.4977	$50.50	$50.50	$50.50
7 purchase totals =	$1,089.42		$1,160.3926	$1,160.39	$1,160.45	$1,160.40