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	$140.54	8.483%	$152.462	$152.46	$152.45	$152.50
Purchase #2	$73.75	10.546%	$81.5277	$81.53	$81.55	$81.50
Purchase #3	$83.60	4.579%	$87.428	$87.43	$87.45	$87.40
Purchase #4	$174.77	9.145%	$190.7527	$190.75	$190.75	$190.80
Purchase #5	$134.82	13.621%	$153.1838	$153.18	$153.20	$153.20
Purchase #6	$176.71	13.519%	$200.5994	$200.60	$200.60	$200.60
Purchase #7	$96.61	13.746%	$109.89	$109.89	$109.90	$109.90
7 purchase totals =	$880.80		$975.8436	$975.84	$975.90	$975.90