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	$158.37	7.447%	$170.1638	$170.16	$170.15	$170.20
Purchase #2	$216.46	6.237%	$229.9606	$229.96	$229.95	$230.00
Purchase #3	$132.79	6.529%	$141.4599	$141.46	$141.45	$141.50
Purchase #4	$49.84	11.511%	$55.5771	$55.58	$55.60	$55.60
Purchase #5	$156.95	12.444%	$176.4809	$176.48	$176.50	$176.50
Purchase #6	$142.55	12.467%	$160.3217	$160.32	$160.30	$160.30
Purchase #7	$106.42	9.472%	$116.5001	$116.50	$116.50	$116.50
7 purchase totals =	$963.38		$1,050.4641	$1,050.46	$1,050.45	$1,050.60