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	$111.67	11.522%	$124.5366	$124.54	$124.55	$124.50
Purchase #2	$56.82	11.819%	$63.5356	$63.54	$63.55	$63.50
Purchase #3	$218.65	3.574%	$226.4646	$226.46	$226.45	$226.50
Purchase #4	$242.93	11.365%	$270.539	$270.54	$270.55	$270.50
Purchase #5	$46.35	10.577%	$51.2524	$51.25	$51.25	$51.30
Purchase #6	$229.95	11.633%	$256.7001	$256.70	$256.70	$256.70
Purchase #7	$66.45	8.869%	$72.3435	$72.34	$72.35	$72.30
7 purchase totals =	$972.82		$1,065.3718	$1,065.37	$1,065.40	$1,065.30