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	$172.66	5.389%	$181.9646	$181.96	$181.95	$182.00
Purchase #2	$250.60	9.553%	$274.5398	$274.54	$274.55	$274.50
Purchase #3	$198.75	12.628%	$223.8482	$223.85	$223.85	$223.80
Purchase #4	$29.40	7.615%	$31.6388	$31.64	$31.65	$31.60
Purchase #5	$124.62	4.683%	$130.456	$130.46	$130.45	$130.50
Purchase #6	$235.54	7.721%	$253.726	$253.73	$253.75	$253.70
Purchase #7	$34.38	3.406%	$35.551	$35.55	$35.55	$35.60
7 purchase totals =	$1,045.95		$1,131.7244	$1,131.73	$1,131.75	$1,131.70