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	$157.91	5.756%	$166.9993	$167.00	$167.00	$167.00
Purchase #2	$237.88	12.130%	$266.7348	$266.73	$266.75	$266.70
Purchase #3	$224.60	7.446%	$241.3237	$241.32	$241.30	$241.30
Purchase #4	$100.49	6.254%	$106.7746	$106.77	$106.75	$106.80
Purchase #5	$76.40	3.209%	$78.8517	$78.85	$78.85	$78.90
Purchase #6	$24.43	11.775%	$27.3066	$27.31	$27.30	$27.30
Purchase #7	$235.81	11.338%	$262.5461	$262.55	$262.55	$262.50
7 purchase totals =	$1,057.52		$1,150.5368	$1,150.53	$1,150.50	$1,150.50