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	$51.89	5.557%	$54.7735	$54.77	$54.75	$54.80
Purchase #2	$146.72	6.620%	$156.4329	$156.43	$156.45	$156.40
Purchase #3	$35.76	6.535%	$38.0969	$38.10	$38.10	$38.10
Purchase #4	$176.30	7.493%	$189.5102	$189.51	$189.50	$189.50
Purchase #5	$238.48	8.464%	$258.6649	$258.66	$258.65	$258.70
Purchase #6	$217.53	8.223%	$235.4175	$235.42	$235.40	$235.40
Purchase #7	$70.49	11.585%	$78.6563	$78.66	$78.65	$78.70
7 purchase totals =	$937.17		$1,011.5522	$1,011.55	$1,011.50	$1,011.60