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	$200.51	12.493%	$225.5597	$225.56	$225.55	$225.60
Purchase #2	$152.58	5.362%	$160.7613	$160.76	$160.75	$160.80
Purchase #3	$40.94	11.420%	$45.6153	$45.62	$45.60	$45.60
Purchase #4	$168.39	10.686%	$186.3842	$186.38	$186.40	$186.40
Purchase #5	$152.34	3.688%	$157.9583	$157.96	$157.95	$158.00
Purchase #6	$48.62	6.797%	$51.9247	$51.92	$51.90	$51.90
Purchase #7	$168.25	3.458%	$174.0681	$174.07	$174.05	$174.10
7 purchase totals =	$931.63		$1,002.2716	$1,002.27	$1,002.20	$1,002.40