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	$115.90	9.616%	$127.0449	$127.04	$127.05	$127.00
Purchase #2	$182.92	9.581%	$200.4456	$200.45	$200.45	$200.40
Purchase #3	$128.74	4.376%	$134.3737	$134.37	$134.35	$134.40
Purchase #4	$135.67	5.836%	$143.5877	$143.59	$143.60	$143.60
Purchase #5	$184.91	7.264%	$198.3419	$198.34	$198.35	$198.30
Purchase #6	$104.96	12.748%	$118.3403	$118.34	$118.35	$118.30
Purchase #7	$125.57	9.810%	$137.8884	$137.89	$137.90	$137.90
7 purchase totals =	$978.67		$1,060.0225	$1,060.02	$1,060.05	$1,059.90