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	$150.64	12.163%	$168.9623	$168.96	$168.95	$169.00
Purchase #2	$179.65	12.367%	$201.8673	$201.87	$201.85	$201.90
Purchase #3	$12.66	10.454%	$13.9835	$13.98	$14.00	$14.00
Purchase #4	$248.89	12.844%	$280.8574	$280.86	$280.85	$280.90
Purchase #5	$196.42	11.298%	$218.6115	$218.61	$218.60	$218.60
Purchase #6	$119.52	3.807%	$124.0701	$124.07	$124.05	$124.10
Purchase #7	$137.78	3.254%	$142.2634	$142.26	$142.25	$142.30
7 purchase totals =	$1,045.56		$1,150.6155	$1,150.61	$1,150.55	$1,150.80