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	$88.51	3.590%	$91.6875	$91.69	$91.70	$91.70
Purchase #2	$107.50	4.798%	$112.6579	$112.66	$112.65	$112.70
Purchase #3	$227.59	4.549%	$237.9431	$237.94	$237.95	$237.90
Purchase #4	$193.80	11.213%	$215.5308	$215.53	$215.55	$215.50
Purchase #5	$188.67	4.475%	$197.113	$197.11	$197.10	$197.10
Purchase #6	$192.87	10.636%	$213.3837	$213.38	$213.40	$213.40
Purchase #7	$116.27	10.284%	$128.2272	$128.23	$128.25	$128.20
7 purchase totals =	$1,115.21		$1,196.5432	$1,196.54	$1,196.60	$1,196.50