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	$140.65	5.630%	$148.5686	$148.57	$148.55	$148.60
Purchase #2	$54.27	4.109%	$56.5	$56.50	$56.50	$56.50
Purchase #3	$109.81	7.574%	$118.127	$118.13	$118.15	$118.10
Purchase #4	$109.91	6.475%	$117.0267	$117.03	$117.05	$117.00
Purchase #5	$51.53	11.226%	$57.3148	$57.31	$57.30	$57.30
Purchase #6	$11.45	9.677%	$12.558	$12.56	$12.55	$12.60
Purchase #7	$150.33	4.757%	$157.4812	$157.48	$157.50	$157.50
7 purchase totals =	$627.95		$667.5763	$667.58	$667.60	$667.60