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	$193.81	3.499%	$200.5914	$200.59	$200.60	$200.60
Purchase #2	$48.81	11.846%	$54.592	$54.59	$54.60	$54.60
Purchase #3	$129.37	6.609%	$137.9201	$137.92	$137.90	$137.90
Purchase #4	$64.45	6.235%	$68.4685	$68.47	$68.45	$68.50
Purchase #5	$201.26	7.627%	$216.6101	$216.61	$216.60	$216.60
Purchase #6	$70.35	10.346%	$77.6284	$77.63	$77.65	$77.60
Purchase #7	$43.44	5.407%	$45.7888	$45.79	$45.80	$45.80
7 purchase totals =	$751.49		$801.5993	$801.60	$801.60	$801.60