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	$38.71	11.464%	$43.1477	$43.15	$43.15	$43.10
Purchase #2	$156.86	3.622%	$162.5415	$162.54	$162.55	$162.50
Purchase #3	$208.75	10.803%	$231.3013	$231.30	$231.30	$231.30
Purchase #4	$226.99	5.801%	$240.1577	$240.16	$240.15	$240.20
Purchase #5	$241.66	13.269%	$273.7259	$273.73	$273.75	$273.70
Purchase #6	$82.82	10.754%	$91.7265	$91.73	$91.75	$91.70
Purchase #7	$39.32	5.374%	$41.4331	$41.43	$41.45	$41.40
7 purchase totals =	$995.11		$1,084.0337	$1,084.04	$1,084.10	$1,083.90