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	$160.80	7.102%	$172.22	$172.22	$172.20	$172.20
Purchase #2	$243.85	10.496%	$269.4445	$269.44	$269.45	$269.40
Purchase #3	$53.30	13.460%	$60.4742	$60.47	$60.45	$60.50
Purchase #4	$57.59	9.366%	$62.9839	$62.98	$63.00	$63.00
Purchase #5	$30.69	13.690%	$34.8915	$34.89	$34.90	$34.90
Purchase #6	$200.76	3.184%	$207.1522	$207.15	$207.15	$207.20
Purchase #7	$184.63	13.131%	$208.8738	$208.87	$208.85	$208.90
7 purchase totals =	$931.62		$1,016.0401	$1,016.02	$1,016.00	$1,016.10