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	$75.86	8.625%	$82.4029	$82.40	$82.40	$82.40
Purchase #2	$63.73	8.612%	$69.2184	$69.22	$69.20	$69.20
Purchase #3	$250.88	12.649%	$282.6138	$282.61	$282.60	$282.60
Purchase #4	$102.94	13.471%	$116.807	$116.81	$116.80	$116.80
Purchase #5	$46.40	6.654%	$49.4875	$49.49	$49.50	$49.50
Purchase #6	$216.72	13.257%	$245.4506	$245.45	$245.45	$245.50
Purchase #7	$80.37	13.177%	$90.9604	$90.96	$90.95	$91.00
7 purchase totals =	$836.90		$936.9406	$936.94	$936.90	$937.00