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	$184.46	6.553%	$196.5477	$196.55	$196.55	$196.50
Purchase #2	$65.25	3.732%	$67.6851	$67.69	$67.70	$67.70
Purchase #3	$127.72	3.313%	$131.9514	$131.95	$131.95	$132.00
Purchase #4	$177.75	5.124%	$186.8579	$186.86	$186.85	$186.90
Purchase #5	$150.29	9.812%	$165.0365	$165.04	$165.05	$165.00
Purchase #6	$16.86	11.738%	$18.839	$18.84	$18.85	$18.80
Purchase #7	$35.50	7.500%	$38.1625	$38.16	$38.15	$38.20
7 purchase totals =	$757.83		$805.0801	$805.09	$805.10	$805.10