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	$192.64	13.290%	$218.2419	$218.24	$218.25	$218.20
Purchase #2	$171.51	11.393%	$191.0501	$191.05	$191.05	$191.10
Purchase #3	$77.46	7.163%	$83.0085	$83.01	$83.00	$83.00
Purchase #4	$98.64	3.310%	$101.905	$101.91	$101.90	$101.90
Purchase #5	$179.60	6.115%	$190.5825	$190.58	$190.60	$190.60
Purchase #6	$73.68	6.710%	$78.6239	$78.62	$78.60	$78.60
Purchase #7	$9.37	12.171%	$10.5104	$10.51	$10.50	$10.50
7 purchase totals =	$802.90		$873.9223	$873.92	$873.90	$873.90