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	$87.96	9.424%	$96.2494	$96.25	$96.25	$96.20
Purchase #2	$78.70	5.623%	$83.1253	$83.13	$83.15	$83.10
Purchase #3	$231.31	10.774%	$256.2313	$256.23	$256.25	$256.20
Purchase #4	$134.54	3.410%	$139.1278	$139.13	$139.15	$139.10
Purchase #5	$160.39	13.557%	$182.1341	$182.13	$182.15	$182.10
Purchase #6	$95.98	8.271%	$103.9185	$103.92	$103.90	$103.90
Purchase #7	$176.75	5.183%	$185.911	$185.91	$185.90	$185.90
7 purchase totals =	$965.63		$1,046.6974	$1,046.70	$1,046.75	$1,046.50