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	$160.97	4.744%	$168.6064	$168.61	$168.60	$168.60
Purchase #2	$169.89	3.639%	$176.0723	$176.07	$176.05	$176.10
Purchase #3	$220.83	3.211%	$227.9209	$227.92	$227.90	$227.90
Purchase #4	$142.87	5.155%	$150.2349	$150.23	$150.25	$150.20
Purchase #5	$51.47	7.149%	$55.1496	$55.15	$55.15	$55.10
Purchase #6	$215.33	12.331%	$241.8823	$241.88	$241.90	$241.90
Purchase #7	$216.25	10.365%	$238.6643	$238.66	$238.65	$238.70
7 purchase totals =	$1,177.61		$1,258.5307	$1,258.52	$1,258.50	$1,258.50