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	$102.91	9.227%	$112.4055	$112.41	$112.40	$112.40
Purchase #2	$138.74	11.766%	$155.0641	$155.06	$155.05	$155.10
Purchase #3	$186.34	5.584%	$196.7452	$196.75	$196.75	$196.70
Purchase #4	$87.76	9.456%	$96.0586	$96.06	$96.05	$96.10
Purchase #5	$140.39	9.779%	$154.1187	$154.12	$154.10	$154.10
Purchase #6	$230.40	12.184%	$258.4719	$258.47	$258.45	$258.50
Purchase #7	$240.39	4.380%	$250.9191	$250.92	$250.90	$250.90
7 purchase totals =	$1,126.93		$1,223.7831	$1,223.79	$1,223.70	$1,223.80