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	$61.72	9.540%	$67.6081	$67.61	$67.60	$67.60
Purchase #2	$201.25	5.642%	$212.6045	$212.60	$212.60	$212.60
Purchase #3	$154.27	8.869%	$167.9522	$167.95	$167.95	$168.00
Purchase #4	$228.54	6.357%	$243.0683	$243.07	$243.05	$243.10
Purchase #5	$150.31	10.789%	$166.5269	$166.53	$166.55	$166.50
Purchase #6	$52.43	10.492%	$57.931	$57.93	$57.95	$57.90
Purchase #7	$72.93	12.269%	$81.8778	$81.88	$81.90	$81.90
7 purchase totals =	$921.45		$997.5688	$997.57	$997.60	$997.60