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	$190.98	3.141%	$196.9787	$196.98	$197.00	$197.00
Purchase #2	$228.92	12.486%	$257.503	$257.50	$257.50	$257.50
Purchase #3	$226.90	6.267%	$241.1198	$241.12	$241.10	$241.10
Purchase #4	$56.69	4.125%	$59.0285	$59.03	$59.05	$59.00
Purchase #5	$145.42	7.593%	$156.4617	$156.46	$156.45	$156.50
Purchase #6	$102.57	13.691%	$116.6129	$116.61	$116.60	$116.60
Purchase #7	$64.31	13.219%	$72.8111	$72.81	$72.80	$72.80
7 purchase totals =	$1,015.79		$1,100.5157	$1,100.51	$1,100.50	$1,100.50