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	$216.63	5.466%	$228.471	$228.47	$228.45	$228.50
Purchase #2	$132.89	11.750%	$148.5046	$148.50	$148.50	$148.50
Purchase #3	$207.52	7.449%	$222.9782	$222.98	$223.00	$223.00
Purchase #4	$12.82	11.256%	$14.263	$14.26	$14.25	$14.30
Purchase #5	$149.43	5.684%	$157.9236	$157.92	$157.90	$157.90
Purchase #6	$229.40	12.666%	$258.4558	$258.46	$258.45	$258.50
Purchase #7	$118.98	10.484%	$131.4539	$131.45	$131.45	$131.50
7 purchase totals =	$1,067.67		$1,162.0501	$1,162.04	$1,162.00	$1,162.20