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	$231.79	13.133%	$262.231	$262.23	$262.25	$262.20
Purchase #2	$241.89	5.603%	$255.4431	$255.44	$255.45	$255.40
Purchase #3	$213.63	13.571%	$242.6217	$242.62	$242.60	$242.60
Purchase #4	$69.59	4.338%	$72.6088	$72.61	$72.60	$72.60
Purchase #5	$102.64	12.715%	$115.6907	$115.69	$115.70	$115.70
Purchase #6	$192.91	3.127%	$198.9423	$198.94	$198.95	$198.90
Purchase #7	$154.65	8.249%	$167.4071	$167.41	$167.40	$167.40
7 purchase totals =	$1,207.10		$1,314.9447	$1,314.94	$1,314.95	$1,314.80