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	$232.84	11.858%	$260.4502	$260.45	$260.45	$260.50
Purchase #2	$134.48	5.295%	$141.6007	$141.60	$141.60	$141.60
Purchase #3	$52.48	8.346%	$56.86	$56.86	$56.85	$56.90
Purchase #4	$50.52	7.585%	$54.3519	$54.35	$54.35	$54.40
Purchase #5	$241.35	4.282%	$251.6846	$251.68	$251.70	$251.70
Purchase #6	$104.96	8.198%	$113.5646	$113.56	$113.55	$113.60
Purchase #7	$156.70	7.459%	$168.3883	$168.39	$168.40	$168.40
7 purchase totals =	$973.33		$1,046.9003	$1,046.89	$1,046.90	$1,047.10