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	$59.86	13.668%	$68.0417	$68.04	$68.05	$68.00
Purchase #2	$52.82	5.799%	$55.883	$55.88	$55.90	$55.90
Purchase #3	$177.96	9.390%	$194.6704	$194.67	$194.65	$194.70
Purchase #4	$182.86	3.258%	$188.8176	$188.82	$188.80	$188.80
Purchase #5	$193.86	13.189%	$219.4282	$219.43	$219.45	$219.40
Purchase #6	$113.82	8.586%	$123.5926	$123.59	$123.60	$123.60
Purchase #7	$150.98	6.562%	$160.8873	$160.89	$160.90	$160.90
7 purchase totals =	$932.16		$1,011.3208	$1,011.32	$1,011.35	$1,011.30