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	$98.73	5.143%	$103.8077	$103.81	$103.80	$103.80
Purchase #2	$235.80	11.448%	$262.7944	$262.79	$262.80	$262.80
Purchase #3	$118.55	7.845%	$127.8502	$127.85	$127.85	$127.90
Purchase #4	$220.53	4.752%	$231.0096	$231.01	$231.00	$231.00
Purchase #5	$52.82	3.650%	$54.7479	$54.75	$54.75	$54.70
Purchase #6	$242.36	5.583%	$255.891	$255.89	$255.90	$255.90
Purchase #7	$28.89	4.783%	$30.2718	$30.27	$30.25	$30.30
7 purchase totals =	$997.68		$1,066.3726	$1,066.37	$1,066.35	$1,066.40