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	$156.50	12.446%	$175.978	$175.98	$176.00	$176.00
Purchase #2	$112.79	9.421%	$123.4159	$123.42	$123.40	$123.40
Purchase #3	$53.34	3.673%	$55.2992	$55.30	$55.30	$55.30
Purchase #4	$5.52	12.497%	$6.2098	$6.21	$6.20	$6.20
Purchase #5	$140.75	7.139%	$150.7981	$150.80	$150.80	$150.80
Purchase #6	$170.48	5.326%	$179.5598	$179.56	$179.55	$179.60
Purchase #7	$43.75	11.587%	$48.8193	$48.82	$48.80	$48.80
7 purchase totals =	$683.13		$740.0801	$740.09	$740.05	$740.10