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	$75.80	3.398%	$78.3757	$78.38	$78.40	$78.40
Purchase #2	$55.60	5.574%	$58.6991	$58.70	$58.70	$58.70
Purchase #3	$160.81	6.596%	$171.417	$171.42	$171.40	$171.40
Purchase #4	$224.84	7.262%	$241.1679	$241.17	$241.15	$241.20
Purchase #5	$126.55	4.225%	$131.8967	$131.90	$131.90	$131.90
Purchase #6	$142.63	12.812%	$160.9038	$160.90	$160.90	$160.90
Purchase #7	$99.28	11.155%	$110.3547	$110.35	$110.35	$110.40
7 purchase totals =	$885.51		$952.8149	$952.82	$952.80	$952.90