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	$42.38	11.455%	$47.2346	$47.23	$47.25	$47.20
Purchase #2	$98.85	6.167%	$104.9461	$104.95	$104.95	$104.90
Purchase #3	$51.70	8.793%	$56.246	$56.25	$56.25	$56.20
Purchase #4	$107.35	4.739%	$112.4373	$112.44	$112.45	$112.40
Purchase #5	$133.66	13.146%	$151.2309	$151.23	$151.25	$151.20
Purchase #6	$230.67	11.388%	$256.9387	$256.94	$256.95	$256.90
Purchase #7	$72.87	7.221%	$78.1319	$78.13	$78.15	$78.10
7 purchase totals =	$737.48		$807.1655	$807.17	$807.25	$806.90