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	$118.98	7.221%	$127.5715	$127.57	$127.55	$127.60
Purchase #2	$59.94	10.499%	$66.2331	$66.23	$66.25	$66.20
Purchase #3	$94.98	4.598%	$99.3472	$99.35	$99.35	$99.30
Purchase #4	$103.51	8.371%	$112.1748	$112.17	$112.15	$112.20
Purchase #5	$205.86	5.189%	$216.5421	$216.54	$216.55	$216.50
Purchase #6	$224.51	10.453%	$247.978	$247.98	$248.00	$248.00
Purchase #7	$41.32	8.386%	$44.7851	$44.79	$44.80	$44.80
7 purchase totals =	$849.10		$914.6318	$914.63	$914.65	$914.60