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	$195.90	3.832%	$203.4069	$203.41	$203.40	$203.40
Purchase #2	$99.43	7.708%	$107.0941	$107.09	$107.10	$107.10
Purchase #3	$133.70	9.606%	$146.5432	$146.54	$146.55	$146.50
Purchase #4	$103.58	12.656%	$116.6891	$116.69	$116.70	$116.70
Purchase #5	$116.48	9.770%	$127.8601	$127.86	$127.85	$127.90
Purchase #6	$132.42	13.366%	$150.1193	$150.12	$150.10	$150.10
Purchase #7	$160.89	4.107%	$167.4978	$167.50	$167.50	$167.50
7 purchase totals =	$942.40		$1,019.2105	$1,019.21	$1,019.20	$1,019.20