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	$83.39	3.741%	$86.5096	$86.51	$86.50	$86.50
Purchase #2	$217.74	3.542%	$225.4524	$225.45	$225.45	$225.50
Purchase #3	$242.39	7.472%	$260.5014	$260.50	$260.50	$260.50
Purchase #4	$68.38	9.555%	$74.9137	$74.91	$74.90	$74.90
Purchase #5	$49.90	12.815%	$56.2947	$56.29	$56.30	$56.30
Purchase #6	$190.67	4.298%	$198.865	$198.87	$198.85	$198.90
Purchase #7	$156.29	7.542%	$168.0774	$168.08	$168.10	$168.10
7 purchase totals =	$1,008.76		$1,070.6142	$1,070.61	$1,070.60	$1,070.70