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	$43.33	10.838%	$48.0261	$48.03	$48.05	$48.00
Purchase #2	$217.83	8.490%	$236.3238	$236.32	$236.30	$236.30
Purchase #3	$215.27	7.585%	$231.5982	$231.60	$231.60	$231.60
Purchase #4	$144.45	3.564%	$149.5982	$149.60	$149.60	$149.60
Purchase #5	$57.43	3.653%	$59.5279	$59.53	$59.55	$59.50
Purchase #6	$185.30	3.562%	$191.9004	$191.90	$191.90	$191.90
Purchase #7	$212.55	6.751%	$226.8993	$226.90	$226.90	$226.90
7 purchase totals =	$1,076.16		$1,143.8739	$1,143.88	$1,143.90	$1,143.80