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	$145.56	5.751%	$153.9312	$153.93	$153.95	$153.90
Purchase #2	$207.46	4.331%	$216.4451	$216.45	$216.45	$216.40
Purchase #3	$168.56	6.201%	$179.0124	$179.01	$179.00	$179.00
Purchase #4	$102.30	9.576%	$112.0962	$112.10	$112.10	$112.10
Purchase #5	$34.31	13.381%	$38.901	$38.90	$38.90	$38.90
Purchase #6	$73.95	6.493%	$78.7516	$78.75	$78.75	$78.80
Purchase #7	$72.29	6.640%	$77.0901	$77.09	$77.10	$77.10
7 purchase totals =	$804.43		$856.2276	$856.23	$856.25	$856.20