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	$194.61	12.565%	$219.0627	$219.06	$219.05	$219.10
Purchase #2	$244.95	7.545%	$263.4315	$263.43	$263.45	$263.40
Purchase #3	$216.37	11.375%	$240.9821	$240.98	$241.00	$241.00
Purchase #4	$90.87	5.731%	$96.0778	$96.08	$96.10	$96.10
Purchase #5	$242.51	13.189%	$274.4946	$274.49	$274.50	$274.50
Purchase #6	$225.78	13.167%	$255.5085	$255.51	$255.50	$255.50
Purchase #7	$141.39	5.802%	$149.5934	$149.59	$149.60	$149.60
7 purchase totals =	$1,356.48		$1,499.1506	$1,499.14	$1,499.20	$1,499.20