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	$168.25	4.359%	$175.584	$175.58	$175.60	$175.60
Purchase #2	$172.29	12.373%	$193.6074	$193.61	$193.60	$193.60
Purchase #3	$58.45	9.467%	$63.9835	$63.98	$64.00	$64.00
Purchase #4	$92.68	8.696%	$100.7395	$100.74	$100.75	$100.70
Purchase #5	$105.52	5.202%	$111.0092	$111.01	$111.00	$111.00
Purchase #6	$39.40	9.317%	$43.0709	$43.07	$43.05	$43.10
Purchase #7	$99.32	13.317%	$112.5464	$112.55	$112.55	$112.50
7 purchase totals =	$735.91		$800.5409	$800.54	$800.55	$800.50