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	$22.42	10.802%	$24.8418	$24.84	$24.85	$24.80
Purchase #2	$233.92	8.815%	$254.54	$254.54	$254.55	$254.50
Purchase #3	$247.86	3.279%	$255.9873	$255.99	$256.00	$256.00
Purchase #4	$241.50	9.229%	$263.788	$263.79	$263.80	$263.80
Purchase #5	$140.46	5.484%	$148.1628	$148.16	$148.15	$148.20
Purchase #6	$81.59	4.572%	$85.3203	$85.32	$85.30	$85.30
Purchase #7	$102.90	9.281%	$112.4501	$112.45	$112.45	$112.50
7 purchase totals =	$1,070.65		$1,145.0903	$1,145.09	$1,145.10	$1,145.10