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	$238.58	11.495%	$266.0048	$266.00	$266.00	$266.00
Purchase #2	$54.39	6.871%	$58.1271	$58.13	$58.15	$58.10
Purchase #3	$55.83	13.378%	$63.2989	$63.30	$63.30	$63.30
Purchase #4	$154.26	6.642%	$164.5059	$164.51	$164.50	$164.50
Purchase #5	$231.87	7.316%	$248.8336	$248.83	$248.85	$248.80
Purchase #6	$96.48	3.781%	$100.1279	$100.13	$100.15	$100.10
Purchase #7	$103.31	11.595%	$115.2888	$115.29	$115.30	$115.30
7 purchase totals =	$934.72		$1,016.1870	$1,016.19	$1,016.25	$1,016.10